regulator: core: Add regulator_is_equal() helper

regulator: core: Add regulator_is_equal() helper

BugLink: https://bugs.launchpad.net/bugs/1867051
commit b059b7e0ec3208ff1e17cff6387d75a9fbab4e02 upstream.

Add regulator_is_equal() helper to compare whether two regulators are
the same. This is useful for checking whether two separate regulators
in a driver are actually the same supply.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Igor Opaniuk <igor.opaniuk@toradex.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
Link: https://lore.kernel.org/r/20191220164450.1395038-1-marex@denx.de
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>