powerpc/64s: Add FA_DUMP to defconfig

FA_DUMP (Firmware Assisted Dump) is a powerpc only feature that should
be enabled in our defconfig to get some build / test coverage.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210420042209.1641634-1-mpe@ellerman.id.au

arch/powerpc/configs/ppc64_defconfig

@@ -50,6 +50,7 @@ CONFIG_PPC_TRANSACTIONAL_MEM=y
 CONFIG_KEXEC=y
 CONFIG_KEXEC_FILE=y
 CONFIG_CRASH_DUMP=y
+CONFIG_FA_DUMP=y
 CONFIG_IRQ_ALL_CPUS=y
 CONFIG_PPC_64K_PAGES=y
 CONFIG_SCHED_SMT=y