spi-generic.h: Adapt include guard

Rename _SPI_H_ to _SPI_GENERIC_H_ to match recent file rename.

Change-Id: I8b75e2e0a515fb540587630163ad289d0a6a0b22
Reported-by: Peter Stuge <peter@stuge.se>
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/2360
Tested-by: build bot (Jenkins)
Reviewed-by: Peter Stuge <peter@stuge.se>
1 file changed