ARM: 6789/1: SPEAr3xx: Rename sdio to sdhci

Device name of SD/MMC/SDIO controller in linux is sdhci. To maintain
consistency across all spear code, rename sdio to sdhci.

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>