ath6kl: Re-architect suspend mode handling in ath6kl_sdio_suspend

Using this patch, the user can bypass existing auto
suspend mode selection logic and force ath6kl to enter
into the suspend mode what he/she wants.

If the user doesn't choose any suspend mode while doing
insmod of the driver, auto suspend mode selection logic
will kick in and choose suspend mode based on the host
SDIO controller capability.

Generic module parameter is required to specify suspend
mode including Deep Sleep and WOW while doing insmod.
Renaming existing mod param variable suspend_cutpower
would be sufficient to meet this requirement.

New module parameter suspend_mode can take any one of
the below suspend state,
   1. cut power
   2. deep sleep
   3. wow

Signed-off-by: Raja Mani <rmani@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>