usb: misc: usb3503: Fix compile error due to incorrect regmap depedency

The USB3503 driver had an incorrect depedency on REGMAP, instead of
REGMAP_I2C.  This caused the build to fail since the necessary regmap
i2c pieces were not available.

Signed-off-by: Matthew Dawson <matthew@mjdsystems.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>