sdhci: build fix: rename SDHCI I/O accessor functions

Unfortunately some architectures #define their read{b,w,l} and
write{b,w,l} I/O accessors which makes the SDHCI I/O accessor functions of
the same names subject to preprocessing.  This leads to the following
compiler error,

In file included from drivers/mmc/host/sdhci.c:26:
drivers/mmc/host/sdhci.h:318:35: error: macro "writel" passed 3 arguments, but takes just 2

Rename the SDHCI I/O functions so that CONFIG_MMC_SDHCI_IO_ACCESSORS can
be enabled for architectures that implement their read{b,w,l} and
write{b,w,l} functions with macros.

Signed-off-by: Matt Fleming <matt@console-pimps.org>
Cc: Zhangfei Gao <zgao6@marvell.com>
Acked-by: Anton Vorontsov <cbouatmailru@gmail.com>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Ben Dooks <ben-linux@fluff.org>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>