UPSTREAM: power: supply: core: Add a macro that maps enum properties to text values

Reduce the number of touch points to add a new enum property to the
power_supply class by mapping the array of text values to the device
attribute descriptor. A new enum property can now added by creating an
array with the text values named POWER_SUPPLY_${PROPNAME}_TEXT and
adding POWER_SUPPLY_ENUM_ATTR(${PROPNAME}) to the power_supply_attrs
array.

Signed-off-by: Mathew King <mathewk@chromium.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
(cherry picked from commit 5b505366ac6c77a623e18fe18cedb2d4d3c9a7f3)
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I6e14c215bd2c2cc39d7649062c238e65d11eabaa