post_code: add post code for failure to load next stage

Add a new post code, POST_INVALID_ROM, used when coreboot fails to
locate or validate a resource that is stored in ROM.

BUG=b:124401932
BRANCH=sarien
TEST=build coreboot for sarien and arcada platforms

Change-Id: Ie6de6590595d8fcdc57ad156237fffa03d5ead38
Signed-off-by: Keith Short <keithshort@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32770
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
diff --git a/Documentation/POSTCODES b/Documentation/POSTCODES
index 5d337b6..2340fac 100644
--- a/Documentation/POSTCODES
+++ b/Documentation/POSTCODES
@@ -16,6 +16,7 @@
 0x66 Devices have been enumerated
 0x88 Devices have been configured
 0x89 Devices have been enabled
+0xe0 Boot media (e.g. SPI ROM) is corrupt
 0xf8 Entry into elf boot
 0xf3 Jumping to payload