spi: qup: Depend on ARM && COMPILE_TEST to avoid build error

This driver uses writel_relaxed() which does not exist in x86, ppc, etc.
Make it depend on ARM && COMPILE_TEST to avoid below build error:

  CC [M]  drivers/spi/spi-qup.o
drivers/spi/spi-qup.c: In function 'spi_qup_set_state':
drivers/spi/spi-qup.c:180:3: error: implicit declaration of function 'writel_relaxed' [-Werror=implicit-function-declaration]
cc1: some warnings being treated as errors
make[2]: *** [drivers/spi/spi-qup.o] Error 1
make[1]: *** [drivers/spi] Error 2
make: *** [drivers] Error 2

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@linaro.org>