soc/amd/cezanne: remove warm reset flag code

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, the
NCP_WARM_BOOT bit never got set and the NCP_ERR register in I/O-space
always reads back as 0x7f.

[1] checked with PPR for AMD Family 19h Model 51h A1 (CZN) #56569 Rev
3.01

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I569372db9f36ec7bbc741f4d7312ade312daa70b
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55101
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/cezanne/cpu.c

@@ -55,8 +55,6 @@ 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 zen_2_3_init(struct device *dev)