regulator: isl9305: deprecate use of isl in compatible string for isil

"isil" and "isl" prefixes are used at various locations inside the kernel
to reference Intersil corporation. This patch is part of a series fixing
those locations were "isl" is used in compatible strings to use the now
expected "isil" prefix instead (NASDAQ symbol for Intersil and most used
version). The old compatible string is kept for backward compatibility.

Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Mark Brown <broonie@kernel.org>