drivers: phy: add PIPE3 phy driver

This phy is found on omap platforms with sata capabilities.
Except for the part related to the DM and the PHY framework, the code is
basically a copy paste from arch/arm/mach-omap2/pipe3-phy.c

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>