reset: simple: Add AST2600 compatible

Similar to the 2400 and 2500, the LPC controller has some simple reset
lines that are used by the UART devices.

This is already documented in LPC bindings document.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20220221072650.129348-1-joel@jms.id.au