spi95: Fix error return code of probe_spi_st95()

Probing methods return 1 for success, 0 if nothing was found or
on error.

Change-Id: I3e6242d24e1cf5fa75100ecc56de721248dca174
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72993
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
1 file changed