powerpc/usb: fix usb CTRL_PHY_CLK_VALID breaks on some platform

Fix checking of CTRL_PHY_CLK_VALID bit break on some platform on which
there is not USB CTRL_PHY_CLK_VALID bit.
  - P1023/P3041/P5020 etc,have this bit
  - P3060/4080/PSC913x do have this bit, but not mentioned in RM.
  - P1022(perhaps and other) has no this bit

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