ARM: OMAP3: am3517_evm: Move header to ti_omap3_common.h

Much of the AM3517 functions are copies of the standard definitions
used in ti_omap3_common.h.  Moving to include a common file
reduces the amount of duplicative code and clutter.  A few
AM3517 specific functions (like EMIF4) are explictly defined
and a few items are undefined or redefined, but overall the number
of lines of code shink.

Signed-off-by: Adam Ford <aford173@gmail.com>
Tested-by: Derald D. Woods <woods.technical@gmail.com>