Properly work with WiFi power states

* MMC_WIFI is now always defined, move wifi-power.c to mach-msm dir
  for now, will be renamed/fixed later.
* Call power control differently depending on the source of the call.
* Introduce new common header for salsa.
Process userspace and dhd module power calls differently

* Drop CONFIG_MMC_WIFI define
* Don't call wifi_set_carddetect when module tries to switch power.
Merge wifi fixes. Closes #1