soc: aspeed: lpc-snoop: Lift channel config to const structs

soc: aspeed: lpc-snoop: Lift channel config to const structs

The shifts and masks for each channel are defined by hardware and
are not something that changes at runtime. Accordingly, describe the
information in an array of const structs and associate elements with
each channel instance, removing the need for the switch and handling of
its default case.

Link: https://patch.msgid.link/20250616-aspeed-lpc-snoop-fixes-v2-10-3cdd59c934d3@codeconstruct.com.au
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>