linux-sony-amami: Backport getrandom to support libressl on linux < 3.17

This fixes (for the Xperia Z1 compact downstream kernel) #107 (closed).
Many thanks to @michitux for the research.
Note: This is in NO way clean or tested extensively. I just kept throwing patches found by google search for "backport getrandom" until the kernel compiled and booted. The only thing that I can confirm is that this fixes https connections in python2 applications for me.