spi25.c: Add function to return opcode of passed erase fucntion pointer

There is a function, spi_get_erasefn_from_opcode, which returns the
erase function for given opcode. Add a function which does the opposite
i.e. returns the opcode for given erase function.

Change-Id: Ia3aefc9b9465efdd16b1678bb2ada9a23f00d316
Signed-off-by: Aarya Chaumal <aarya.chaumal@gmail.com>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/65355
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Original-Reviewed-by: Thomas Heijligen <src@posteo.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72538
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
2 files changed