UPSTREAM: mwifiex: update max_chan_per_scan correctly for SSID scan

UPSTREAM: mwifiex: update max_chan_per_scan correctly for SSID scan

As per recent patch "658f37b mwifiex: scan less channels..."
less channels are scanned per scan command in associated state.

Default number of channels per scan command for normal scan are
already 4, but those are 14 for SSID specific scan operation.

This code change in this patch is required for SSID specific scan.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
This patch has been submitted to wireless-testing.git and expected
in upstream shortly.

BUG=chrome-os-partner:11597
TEST=Run autotest WiFiMatFunc.090_BgScanBackoff and pass the test

Change-Id: Ie5decec777e91ca28d36dbe366a7ec6c8677b434
Reviewed-on: https://gerrit.chromium.org/gerrit/29230
Reviewed-by: Sam Leffler <sleffler@chromium.org>
Commit-Ready: Bing Zhao <bzhao@marvell.com>
Tested-by: Bing Zhao <bzhao@marvell.com>