imx-usb-loader: fix build with older gcc

imx-usb-loader: fix build with older gcc

Since the last version bump imx-usb-loader uses __builtin_bswap16 which
is not universally available in gcc older than version 4.8. Add a patch
switching to a local 16-bit bytes swap implementation.

Should fix:
http://autobuild.buildroot.net/results/a63/a63b593b7ef3b6d32e755afe42b77d47dbf0276e/
http://autobuild.buildroot.net/results/48c/48c95cfc65f99fa02be81a11303ba8999f57091a/
http://autobuild.buildroot.net/results/c9d/c9d4f99b49ddb9b2ce08fce7672dd7c70cf62912/

Cc: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>