powerpc/usb: remove checking PHY_CLK_VALID for UTMI PHY

PHY_CLK_VALID bit doesn't work properly with UTMI PHY.
e.g. This bit is always zero on P5040, etc.
There is no need to check this bit for UTMI PHY, just keep
checking for ULPI PHY to prevent system hanging.

This patch should be squashed into previous commit 3735ba8d
"powerpc/usb: fix bug of CPU hang when missing USB PHY clock"

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>