usb: host: imx21-hcd: Remove the driver

Since commit 4b563a06 ("ARM: imx: Remove imx21 support") the imx21
SoC is no longer supported.

Get rid of its USB driver too, which is now unused.

Acked-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20201109210813.21382-1-festevam@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>