spi: spi-mxs: fix reference leak to master in mxs_spi_remove()

Once a spi_master_get() call succeeds, we need an additional
spi_master_put() call to free the memory, otherwise we will
leak a reference to master. Fix by removing the unnecessary
spi_master_get() call.

Fixes: 33e195ac ('spi: mxs: use devm_spi_register_master()')
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Mark Brown <broonie@linaro.org>