generic: add missing Kconfig symbol ARM_SCMI_PROTOCOL

Add the missing ARM_SCMI_PROTOCOL symbol. Apparently it was exposed
for 5.10.53 with a kernel dependency change.
Missing symbol observed with mediatek/7622 E8450/RT3200 router.

Signed-off-by: Hannu Nyman <[email protected]>

target/linux/generic/config-5.10

@@ -397,6 +397,7 @@ CONFIG_ARM_GIC_MAX_NR=1
 # CONFIG_ARM_PSCI_CPUIDLE is not set
 # CONFIG_ARM_PTDUMP_DEBUGFS is not set
 # CONFIG_ARM_SBSA_WATCHDOG is not set
+# CONFIG_ARM_SCMI_PROTOCOL is not set
 # CONFIG_ARM_SCPI_PROTOCOL is not set
 # CONFIG_ARM_SDE_INTERFACE is not set
 # CONFIG_ARM_SMCCC_SOC_ID is not set