mwifiex: Remove custom world regulatory domain

A custom regulatory domain was introduced in this commit:
cc0ba0d5 mwifiex: support custom world regulatory domain

The commit description says that it was introduced because the world
regulatory domain does not include channels 52-64 and 100-140. These
channels are described in the world regulatory domain now, so we can
drop this custom regulatory domain.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Acked-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>