ARM: am3517_evm: Fix pin muxing to enable EHCI Host in the future

This patch enables the pinmuxing to support gpio_57 for phy reset
and fixes the pinmuxing for the ECHI tranceiver.  The clocks
don't appear to by fully enabled yet, so OMAP-EHCI on am3517 is
still not yet working, but we're one step closer.

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