Fix wrong sdhci host control register read and write

The patch fixes the improper read and write of sdhci
host control register for sdma transfer.

The problem comes when reading and writing 1 byte long
host control register with the sdhci_readl() and
sdhci_writel(). The misuse of these functions overwrite
the value of the next registers which are in 4 bytes boundary.

This patch replaces four byte register read/write functions
with one byte read/write ones. Beside, it eliminates
unnecessary bit operation. i.e. or-ing zero against a variable.

Signed-off-by: Juhyun (Justin) Oh <Juhyun_Oh@sigmadesigns.com>