post_code: add post code for hardware initialization failure

Add a new post code POST_HW_INIT_FAILURE, used when coreboot fails to
detect or initialize a required hardware component.

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

Change-Id: I73820d24b3e1c269d9d446a78ef4f97e167e3552
Signed-off-by: Keith Short <keithshort@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32774
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

Documentation/POSTCODES

@@ -20,6 +20,7 @@ This is an (incomplete) list of POST codes emitted by coreboot v4.
 0xe1 Resource stored within CBFS is corrupt
 0xe2 Vendor binary (e.g. FSP) generated a fatal error
 0xe3 RAM could not be initialized
+0xe4 Critical hardware component could not initialize
 0xf8 Entry into elf boot
 0xf3 Jumping to payload