regmap-irq: Introduce virtual regs to handle more config regs

Add "virtual" registers support to handle any irq configuration
registers in addition to the ones the framework currently supports
(status, mask, unmask, wake, type and ack). These are non-standard
registers that further configure irq type on some devices, so enable the
framework to add a variable number of them.

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Link: https://lore.kernel.org/r/a1787067004b0e11cb960319082764397469215a.1616613838.git.gurus@codeaurora.org


Signed-off-by: Mark Brown <broonie@kernel.org>