firmware: revamp firmware documentation

Understanding this code is getting out of control without any
notes. Give the firmware_class driver a much needed documentation love,
and while at it convert it to the new sphinx documentation format.

v2: typos and small fixes

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/driver-api/firmware/index.rst

@@ -0,0 +1,16 @@
+==================
+Linux Firmware API
+==================
+
+.. toctree::
+
+   introduction
+   core
+   request_firmware
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`