clk: davinci: psc-da830: fix USB0 48MHz PHY clock registration

USB0 48MHz PHY clock registration fails on DA830 because the
da8xx-cfgchip clock driver cannot get a reference to USB0
LPSC clock.

The USB0 LPSC needs to be enabled during PHY clock enable. Setup
the clock lookup correctly to fix this.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Reviewed-by: David Lechner <david@lechnology.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>