ARM: omap3_logic: Refactor Boot Environmental variables

Some scripts are calling the same functions, so these changes consolidate
common scripts together to reduce redundancy and shrink size a bit.  This
also keeps the 'bootargs' variable from growing if manually called more
than one time. This also adds NAND booting scripts based on newly consolidated
scripts.

Signed-off-by: Adam Ford <aford173@gmail.com>