omap3630: Set omap3630 MMC1 I/O speed to 52Mhz

The speed ctrl bit for MMC I/O is part of CONTROL_PROG_IO1 register
in omap3630.This patch sets it up accordingly.

Signed-off-by: Madhusudhan Chikkature <madhu.cr@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>