Clean up some confusion of implicit copies by indirection.
This allows the caller of register_spi_master() to have it's
internal state in the expected way.

Also add an error when the mpu reset fails on init.

BUG=b:148746232,b:153027771,b:140394053
BRANCH=none
TEST=builds

Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Change-Id: I66ba4ffeb696309b8ad5b5ba58650630e8feefa9
Reviewed-on: https://review.coreboot.org/c/flashrom/+/40470


Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>