mwifiex: modify mwifiex_is_pattern_supported() routine

It is modified so that it can be reused for coalesce feature.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>