Check for null pointer before usage of prop.
Coverity Reports -
CID 394590: (#1 of 1): Dereference null return value (NULL_RETURNS)
6. dereference: Dereferencing a pointer that might be NULL prop when
calling fdt_setprop.
Change-Id: I2f864a1b476ef4a22f34d8157e1176354b996172
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
4fc702624c