phy: sun9i-usb: fix error handling

This is likely that checking 'phy->hsic_clk' instead of 'phy->clk' is
expected here.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>