MFC r312995:

MFC r312995:

Initialize a stack variable in mprsas_get_sas_address_for_sata_disk

Thought it's difficult to reproduce, I think this variable was responsible
for a use-after-free panic when a SATA disk timed out responding to a SATA
identify command during boot.

Submitted by:	slm
Reviewed by:	slm
MFC after:	4 weeks
Sponsored by:	Spectra Logic Corp
Differential Revision:	https://reviews.freebsd.org/D9364

git-svn-id: svn://svn.freebsd.org/base/stable/10@314440 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f