misc: sgi-gru: use explicitly signed char

With char becoming unsigned by default, and with `char` alone being
ambiguous and based on architecture, signed chars need to be marked
explicitly as such. This fixes warnings like:

drivers/misc/sgi-gru/grumain.c:711 gru_check_chiplet_assignment() warn: 'gts->ts_user_chiplet_id' is unsigned

Cc: Dimitri Sivanich <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Jason A. Donenfeld <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/sgi-gru/grumain.c

···
  * Optionally, build an array of chars that contain the bit numbers allocated.
  */
 static unsigned long reserve_resources(unsigned long *p, int n, int mmax,
-				       char *idx)
+				       signed char *idx)
 {
 	unsigned long bits = 0;
 	int i;
···
 }
 
 unsigned long gru_reserve_cb_resources(struct gru_state *gru, int cbr_au_count,
-				       char *cbmap)
+				       signed char *cbmap)
 {
 	return reserve_resources(&gru->gs_cbr_map, cbr_au_count, GRU_CBR_AU,
 				 cbmap);
 }
 
 unsigned long gru_reserve_ds_resources(struct gru_state *gru, int dsr_au_count,
-				       char *dsmap)
+				       signed char *dsmap)
 {
 	return reserve_resources(&gru->gs_dsr_map, dsr_au_count, GRU_DSR_AU,
 				 dsmap);

drivers/misc/sgi-gru/grutables.h

···
 	pid_t			ts_tgid_owner;	/* task that is using the
 						   context - for migration */
 	short			ts_user_blade_id;/* user selected blade */
-	char			ts_user_chiplet_id;/* user selected chiplet */
+	signed char		ts_user_chiplet_id;/* user selected chiplet */
 	unsigned short		ts_sizeavail;	/* Pagesizes in use */
 	int			ts_tsid;	/* thread that owns the
 						   structure */
···
 						   required for contest */
 	unsigned char		ts_cbr_au_count;/* Number of CBR resources
 						   required for contest */
-	char			ts_cch_req_slice;/* CCH packet slice */
-	char			ts_blade;	/* If >= 0, migrate context if
+	signed char		ts_cch_req_slice;/* CCH packet slice */
+	signed char		ts_blade;	/* If >= 0, migrate context if
 						   ref from different blade */
-	char			ts_force_cch_reload;
-	char			ts_cbr_idx[GRU_CBR_AU];/* CBR numbers of each
+	signed char		ts_force_cch_reload;
+	signed char		ts_cbr_idx[GRU_CBR_AU];/* CBR numbers of each
 							  allocated CB */
 	int			ts_data_valid;	/* Indicates if ts_gdata has
 						   valid data */
···
 		int cbr_au_count, int dsr_au_count,
 		unsigned char tlb_preload_count, int options, int tsid);
 extern unsigned long gru_reserve_cb_resources(struct gru_state *gru,
-		int cbr_au_count, char *cbmap);
+		int cbr_au_count, signed char *cbmap);
 extern unsigned long gru_reserve_ds_resources(struct gru_state *gru,
-		int dsr_au_count, char *dsmap);
+		int dsr_au_count, signed char *dsmap);
 extern vm_fault_t gru_fault(struct vm_fault *vmf);
 extern struct gru_mm_struct *gru_register_mmu_notifier(void);
 extern void gru_drop_mmu_notifier(struct gru_mm_struct *gms);