tree/: Convert flashchip probe func ptr to enumerate

This forges the way for flashchips.c to be pure declarative
data and lookup functions for dispatch to be pure. This
means that the flashchips data could be extracted out to
be agnostic data of the flashrom code and algorithms.

TEST='R|W|E && --flash-name' on ARM, AMD & Intel DUT's.

Change-Id: I00aaab9c83f305cd47e78c36d9c2867f2b73c396
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/66781
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nikolai Artemiev <nartemiev@google.com>
Reviewed-by: Felix Singer <felixsinger@posteo.net>

tests/spi25.c

@@ -31,7 +31,7 @@ struct flashchip mock_chip = {
 	.total_size	= 0,
 	.page_size	= 256,
 	.tested		= TEST_BAD_PREW,
-	.probe		= probe_spi_rdid,
+	.probe		= PROBE_SPI_RDID,
 	.write		= NULL,
 };