usb: phy: correct the am335x phy header filename

The filename of am35x-phy-control.h is confusing. The header is used
by the am335x phy driver, but the filename refers to am35x. Even worse
there is indeed another device called am35x but it does not use this
header at all.

Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>