staging: regulator: hi6421v600-regulator: add a driver-specific debug macro

Using dev_dbg() is not too nice, as, instead of printing the
name of the regulator, it prints "regulator.<number>", making
harder to associate what is happening with each ldo line.

So, add a debug-specific macro, which will print the rdev's
name, just like the regulator core.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/1690b8531b23910aa915bd2725410b926022c481.1597647359.git.mchehab+huawei@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>