soc/amd/common/cpu/noncar: report 100 MHz external clock in smbios

All AMD SoCs from family 17h on, so all using a non-CAR configuration
to boot, have a reference clock of 100 MHz, so report this for all of
them in the SMBIOS tables.

Change-Id: I9573cbb8ec816c797314415d0c60c72abf23a094
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/86690
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/common/block/cpu/noncar/cpu.c

@@ -26,6 +26,11 @@ unsigned int smbios_processor_family(struct cpuid_result res)
 	return 0x6b; /* Zen */
 }
 
+unsigned int smbios_processor_external_clock(void)
+{
+	return 100; /* 100 MHz */
+}
+
 void set_cstate_io_addr(void)
 {
 	msr_t cst_addr;