scsi: sd: Make protection lookup tables static and relocate functions

Currently the protection lookup tables in sd_prot_flag_mask() and
sd_prot_op() are declared as non-static. As such, they will be rebuilt for
each respective function call.

Optimise by making them static.

This saves ~100B object code for sd.c:

Before:
   text	   data	    bss	    dec	    hex	filename
  25403	   1024	     16	  26443	   674b	drivers/scsi/sd.o

After:
  text	   data	    bss	    dec	    hex	filename
  25299	   1024	     16	  26339	   66e3	drivers/scsi/sd.o

In addition, since those same functions are declared in sd.h, but each are
only referenced in sd.c, relocate them to that same c file.

The inline specifier is dropped also, since gcc should be able to make the
decision to inline.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>