mwifiex: don't drop carrier flag over suspend

If the system suspends with mwifiex wifi powered on, and is then woken
by an ICMP ping packet, the ping response is discarded by the kernel
because the kernel incorrectly thinks there is no carrier.

I can't see any valid reason to want to report loss of carrier here,
so remove the offending code.

Fixes http://dev.laptop.org/ticket/12554

Signed-off-by: Daniel Drake <dsd@laptop.org>
Acked-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>