USB host i.MX21: remove dependency on MACH_MX21

the MACH_MX* macros are scheduled for removal, so just depend
on ARCH_MXC instead. The Kconfig text makes it clear on which
SoC the driver runs on.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/Kconfig

@@ -544,11 +544,11 @@ config USB_HWA_HCD
 	  will be called "hwa-hc".
 
 config USB_IMX21_HCD
-       tristate "iMX21 HCD support"
-       depends on USB && ARM && MACH_MX21
+       tristate "i.MX21 HCD support"
+       depends on USB && ARM && ARCH_MXC
        help
          This driver enables support for the on-chip USB host in the
-         iMX21 processor.
+         i.MX21 processor.
 
          To compile this driver as a module, choose M here: the
          module will be called "imx21-hcd".