scsi: ufs: Fix -Wsometimes-uninitialized warning

scsi: ufs: Fix -Wsometimes-uninitialized warning

clang complains about a possible code path in which a variable is used
without an initialization:

drivers/scsi/ufs/ufshcd.c:7690:3: error: variable 'sdp' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
                BUG_ON(1);
                ^~~~~~~~~
include/asm-generic/bug.h:63:36: note: expanded from macro 'BUG_ON'
 #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
                                   ^~~~~~~~~~~~~~~~~~~

Turn the BUG_ON(1) into an unconditional BUG() that makes it clear to clang
that this code path is never hit.

Link: https://lore.kernel.org/r/20201203223137.1205933-1-arnd@kernel.org
Fixes: 4f3e900b6282 ("scsi: ufs: Clear UAC for FFU and RPMB LUNs")
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>