soc/amd/picasso: remove warm reset flag code

Since the MCA(X) registers have defined values on the cold boot path,
the is_warm_reset check can be dropped. Also the warm reset bit in the
NCP_ERR register doesn't behave as the PPR [1] suggested; no matter if
something was written to the register or the machine went through a warm
reset cycle, the NCP_WARM_BOOT bit never got set.

[1] checked with PPR for AMD Family 17h Models 11h,18h B1 (RV,PCO)
#55570 Rev 3.15

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I4e6df98ffd5d15ca204c9847a76c19c753726737
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55059
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

src/soc/amd/picasso/cpu.c

@@ -59,8 +59,6 @@ void mp_init_cpus(struct bus *cpu_bus)
 
 	/* pre_mp_init made the flash not cacheable. Reset to WP for performance. */
 	mtrr_use_temp_range(FLASH_BASE_ADDR, CONFIG_ROM_SIZE, MTRR_TYPE_WRPROT);
-
-	set_warm_reset_flag();
 }
 
 static void model_17_init(struct device *dev)