USB: ehci-au1xxx.c: use platform_get_resource() and resource_size()

Use platform_get_resource() to fetch the memory resource and
resource_size() for calculate the length.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>