Linux 4.8-stable - spidev_test fails to build with musl libc (fixed in 4.9)

[Ralph Sennhauser]

Hi Greg,

For Linux 4.8 spidev_test.c fails to compile using musl libc, this was
fixed in 4.9 by commit 8736f8022e532a3c1d8873aac78e1113c6ffc3b9 (spi:
spidev_test: fix build with musl libc).

Please consider cherry-picking the above commit for 4.8-stable.

Thanks
Ralph