ANDROID: Enable CONFIG_SMP for riscv configurations

The SMP config is enabled by default for ARM boards. Enable it for
RISCV boards as well to allow for multiple cores.

Bug: 274541879
Fixes: google/android-riscv64#79
Test: Boot on emulator with --cpus=4, confirmed 4 CPUs in /proc/cpuinfo.
Signed-off-by: Prashanth Swaminathan <prashanthsw@google.com>
Change-Id: Ic39284157ca5be59bee1ac2ce05b38c5d6b77ad5

Author: prashanthswami

arch/riscv/configs/gki.config

@@ -1,3 +1,4 @@
 CONFIG_CPU_FREQ=y
 CONFIG_GPIOLIB=y
 # CONFIG_KASAN is not set
+CONFIG_SMP=y