ASoC: uniperf: Add missing __iomem annotation

base referes to a iomem region, so it should have the __iomem annotation.
Fixes the following warnings from sparse:

	sound/soc/sti/sti_uniperif.c:169:19: warning: incorrect type in
		assignment (different address spaces)
	sound/soc/sti/sti_uniperif.c:169:19:    expected void *base
	sound/soc/sti/sti_uniperif.c:169:19:    got void [noderef] <asn:2>*
	sound/soc/sti/uniperif_player.c:104:18: warning: incorrect type in
		argument 1 (different address spaces)
	sound/soc/sti/uniperif_player.c:104:18:    expected void const volatile
		[noderef] <asn:2>*addr
	sound/soc/sti/uniperif_player.c:104:18:    got void *
	[...]

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Signed-off-by: Mark Brown <broonie@kernel.org>