ARM: OMAP4: Panda: rework DMM logic

Part of DMM logic is reuse from commit
47a4bea6 ("ARM: omap4: Update sdram
setting for panda rev A6") Which broke SDP4430 with ES2.3 (uses old
DDR).

So, to maintain support for newer DDR used in Panda ES rev B3, we
should, in addition to the commit
675cc77a ("ARM:OMAP4+: panda-es: Support
Rev B3 Elpida DDR2 RAM"), DDR timings, also do DMM configuration
specific to Panda.

Signed-off-by: Nishanth Menon <nm@ti.com>