USB: fix occasional ULPI timeouts with ehci-mxc

On various mxc boards, the intial ULPI reads resulted in a timeout
which prevented the transceiver to be identified and thus the ehci
device to be probed.

Initializing the hardware lines connected to the transceiver (through
pdata->init call) before actually enabling clocks and configuring
registers in the devices fixes this problem.

Signed-off-by: Valentin Longchamp <valentin.longchamp@epfl.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>