flashrom: Slight restructure of SPI probe_ functions
Preparation for a probe optimization patch. This patch does not change any
functionality. spi_probe_rdid was tested to still work on my M57SLI rev 2.
The idea is to have error checks return error immediately when something
fails, rather than having code inside an if block where the condition
tests for success.
This means: Less indentation, more clear what the code is checking.
Signed-off-by: Peter Stuge <email@example.com>
Acked-by: Ward Vandewege <firstname.lastname@example.org>