Do not destroy input buffer of the OF_getencprop() function on error

Currently when the OF_getprop() function returns with error,
the caller (OF_getencprop()) still changes the buffer endiannes.
This may destroy the default value passed in the input buffer if
used on a Little Endian platform.

Reviewed by: mmel
Submitted by: Zbigniew Bodek <zbb@semihalf.com>
Obtained from: Semihalf
Sponsored by: Cavium