scsi: mpi3mr: Avoid possible run-time warning with long manufacturer strings

The prior use of strscpy() here expected the manufacture_reply strings to
be NUL-terminated, but it is possible they are not, as the code pattern
here shows, e.g., edev->vendor_id being exactly 1 character larger than
manufacture_reply->vendor_id, and the strscpy() was copying only up to
the size of the source character array. Replace this with memtostr(),
which is the unambiguous way to convert a maybe not-NUL-terminated
character array into a NUL-terminated string.

Fixes: 2bd37e28

 ("scsi: mpi3mr: Add framework to issue MPT transport cmds")
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240410023155.2100422-4-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>