drm/r128: Fix undefined behavior due to shift overflowing the constant

Fix:

drivers/gpu/drm/r128/r128_cce.c: In function ‘r128_do_init_cce’:
drivers/gpu/drm/r128/r128_cce.c:417:2: error: case label does not reduce to an integer constant
case R128_PM4_64BM_64VCBM_64INDBM:
^~~~
drivers/gpu/drm/r128/r128_cce.c:418:2: error: case label does not reduce to an integer constant
case R128_PM4_64PIO_64VCPIO_64INDPIO:
^~~~

See https://lore.kernel.org/r/[e-mail] for the gory
details as to why it triggers with older gccs only.

Reviewed-by: Randy Dunlap <[e-mail]>
Signed-off-by: Borislav Petkov <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Alex Deucher <[e-mail]>
Cc: [e-mail]
Signed-off-by: Daniel Vetter <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/r128/r128_drv.h

···
 #	define R128_PM4_64PIO_128INDBM		(5  << 28)
 #	define R128_PM4_64BM_128INDBM		(6  << 28)
 #	define R128_PM4_64PIO_64VCBM_64INDBM	(7  << 28)
-#	define R128_PM4_64BM_64VCBM_64INDBM	(8  << 28)
-#	define R128_PM4_64PIO_64VCPIO_64INDPIO	(15 << 28)
+#	define R128_PM4_64BM_64VCBM_64INDBM	(8U  << 28)
+#	define R128_PM4_64PIO_64VCPIO_64INDPIO	(15U << 28)
 #	define R128_PM4_BUFFER_CNTL_NOUPDATE	(1  << 27)
 
 #define R128_PM4_BUFFER_WM_CNTL		0x0708