msm: board-msm7627a-wlan: Fix wlan gpio request failures in FFA platform

gpio request failures are seen in 7x27a FFA + AR600x wlan
chip combination while bringing WLAN down. The root cause is,
msm_AR600X_shutdown_power() function is trying to request
gpio line (gpio_wlan_sys_rest_en) which is already requested
in msm_AR600X_setup_power().

This patch removes gpio_request for 'gpio_wlan_sys_rest_en'
call in msm_AR600X_shutdown_power() and introduces new flag
'wlan_powered_up' to track wlan power on status.

In addition, Added new condition in msm_AR600X_setup_power()
and msm_AR600X_shutdown_power() function to perform
gpio_free(gpio_wlan_sys_rest_en) only for relevant platforms.

CRs-Fixed: 401855
Change-Id: I7123c5acffa86962999688dc715348e98a020553
Signed-off-by: Antony Thomas <athomas@codeaurora.org>