OMAP3 SDRC: add support for 2 SDRAM chip selects

Some OMAP3 boards (Beagle Cx, Overo, RX51, Pandora) have 2
SDRAM parts connected to the SDRC.

This patch adds the following:
- add a new argument of type omap_sdrc_params struct*
to omap2_init_common_hw and omap2_sdrc_init for the 2nd CS params
- adapted the OMAP boards files to the new prototype of
omap2_init_common_hw
- add the SDRC 2nd CS registers offsets defines
- adapt the sram sleep code to configure the SDRC for the 2nd CS

Note: If the 2nd param to omap2_init_common_hw is NULL, then the
parameters are not programmed into the SDRC CS1 registers

Tested on 3430 SDP and Beagleboard rev C2 and B5, with
suspend/resume and frequency changes (cpufreq).

Signed-off-by: Jean Pihet <jpihet@mvista.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>