powerpc/qe: Fix Kconfig enablement of QE_USB support

Commit 193ab2a changed the USB gadget
Kconfig symbol from USB_GADGET_FSL_QE to USB_FSL_QE, but did not update
the associated symbol name in qe_lib to match.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/sysdev/qe_lib/Kconfig

@@ -22,6 +22,6 @@ config UCC
 
 config QE_USB
 	bool
-	default y if USB_GADGET_FSL_QE
+	default y if USB_FSL_QE
 	help
 	  QE USB Controller support