spi: omap-uwire: Fix build error

Fixes the following build error introduced by commit b3f6a575
("spi: omap-uwire: use devm_ functions"):
drivers/spi/spi-omap-uwire.c:465:2: error: implicit declaration of function ‘devm_ioremap’

Since we are including <linux/io.h>, <asm/io.h> is no longer
needed. Remove it.

Signed-off-by: Sachin Kamat <sachin.kamat@samsung.com>
Signed-off-by: Mark Brown <broonie@linaro.org>