[SCSI] pmcraid: remove duplicate struct member

[SCSI] pmcraid: remove duplicate struct member

sense_buffer is both a direct member of struct pmcraid_cmd as well as
an indirect one via an anonymous union and struct.  Fix this clash by
eliminating the direct member in favour of the anonymous struct/union
one.  The name duplication apparently isn't noticed by gcc versions
earlier than 4.4

Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Anil Ravindranath <anil_ravindranath@pmc-sierra.com>
Cc: Stable Tree <stable@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>