scsi: message: fusion: struct _CONFIG_PAGE_IOC_4: Replace 1-element array with flexible array

Replace the deprecated[1] use of a 1-element array in struct
_CONFIG_PAGE_IOC_4 with a modern flexible array.

Additionally add __counted_by annotation since SEP is only ever accessed
after updating ACtiveSEP:

lsi/mpi_cnfg.h: IOC_4_SEP SEP[] __counted_by(ActiveSEP); /* 08h */
mptsas.c: ii = IOCPage4Ptr->ActiveSEP++;
mptsas.c: IOCPage4Ptr->SEP[ii].SEPTargetID = id;
mptsas.c: IOCPage4Ptr->SEP[ii].SEPBus = channel;

No binary differences are present after this conversion.

Link: https://github.com/KSPP/linux/issues/79 [1]
Signed-off-by: Kees Cook <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Gustavo A. R. Silva <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/message/fusion/lsi/mpi_cnfg.h

···
 } IOC_4_SEP, MPI_POINTER PTR_IOC_4_SEP,
   Ioc4Sep_t, MPI_POINTER pIoc4Sep_t;
 
-/*
- * Host code (drivers, BIOS, utilities, etc.) should leave this define set to
- * one and check Header.PageLength at runtime.
- */
-#ifndef MPI_IOC_PAGE_4_SEP_MAX
-#define MPI_IOC_PAGE_4_SEP_MAX              (1)
-#endif
-
 typedef struct _CONFIG_PAGE_IOC_4
 {
     CONFIG_PAGE_HEADER          Header;                         /* 00h */
     U8                          ActiveSEP;                      /* 04h */
     U8                          MaxSEP;                         /* 05h */
     U16                         Reserved1;                      /* 06h */
-    IOC_4_SEP                   SEP[MPI_IOC_PAGE_4_SEP_MAX];    /* 08h */
+    IOC_4_SEP                   SEP[] __counted_by(ActiveSEP);  /* 08h */
 } CONFIG_PAGE_IOC_4, MPI_POINTER PTR_CONFIG_PAGE_IOC_4,
   IOCPage4_t, MPI_POINTER pIOCPage4_t;