msm8974: Implemented a new api pm8x41_get_pon_reason()

pm8x41_get_pon_reason() returns the power on reason by reading
the PMIC register PON_PON_REASON1.

Change-Id: I0260978a339e3058e089cff5da664d276c55f3b8
diff --git a/dev/pmic/pm8x41/pm8x41.c b/dev/pmic/pm8x41/pm8x41.c
index 62014ad..64aecae 100644
--- a/dev/pmic/pm8x41/pm8x41.c
+++ b/dev/pmic/pm8x41/pm8x41.c
@@ -350,3 +350,7 @@
 	return REG_READ(REVID_REVISION4);
 }
 
+uint8_t pm8x41_get_pon_reason()
+{
+	return REG_READ(PON_PON_REASON1);
+}