Driver uses preprocessor directives to define SLP_ASLEEP and
SLP_ACTIVE. These can be defined using an enumeration type. Doing so
adds to the readability and gives the usual compiler benefits of
having an enum. Functions that currently accept integer types can now
use the new enumeration type, further aiding readability.

Add enumeration type sleep_mode_type. Update code that handles sleep
mode to use the new enumeration type.
Signed-off-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>