platform/x86: Remove "WMAA" from identifier names in wmaa-backlight-wmi.c

The "wmaa" in the name of the wmaa-backlight-wmi driver was named after
the ACPI method handle for EC-based backlight control on the systems
this driver was tested on during development. However, this "WMAA"
handle is generated by the WMI compilation process, and isn't actually
a part of the backlight control mechanism which this driver supports.
Since the "WMAA" handle isn't actually a part of the firmware backlight
interface, the various identifiers in this driver using "WMAA" or
"wmaa" aren't actually appropriate.

As a common denominator across the systems supported by this driver is
that they are hybrid graphics systems with NVIDIA GPUs, using "nvidia"
in the driver name seems more appropriate than "wmaa". Update the
driver to remove "wmaa" and "WMAA" in identifier names where they
appear. The kerneldoc comments for the enum wmi_brightness_method
values are replaced with the verbatim text from the decompiled BMF code
for this WMI class.
Signed-off-by: Daniel Dadap <ddadap@nvidia.com>
Link: https://lore.kernel.org/r/20210927202359.13684-1-ddadap@nvidia.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>