defconfig: Enable mailbox on msm8953

Enable mailbox which is needed for PIL compilation on msm8953.

Change-Id: Ib3d726cc65edb0667eb1d8a5457485f669458099
Signed-off-by: Kyle Yan <kyan@codeaurora.org>
diff --git a/arch/arm64/configs/msm8953-perf_defconfig b/arch/arm64/configs/msm8953-perf_defconfig
index cd7520d..4e7fe31 100644
--- a/arch/arm64/configs/msm8953-perf_defconfig
+++ b/arch/arm64/configs/msm8953-perf_defconfig
@@ -391,6 +391,7 @@
 CONFIG_USB_BAM=y
 CONFIG_QCOM_MDSS_PLL=y
 CONFIG_REMOTE_SPINLOCK_MSM=y
+CONFIG_MAILBOX=y
 CONFIG_ARM_SMMU=y
 CONFIG_MSM_BOOT_STATS=y
 CONFIG_QCOM_EUD=y