feat(rtc): rtc driver implementation initial setup

[Koichi98]

Description

Implemented rtc driver. This is a initial PR to prepare some register constants and the fundamental functions used.
mc146818 is the real time clock broadly used in x86 architecture, and I've checked that I could successfully get the time.

Related links

mc146818_read
https://github.com/openbsd/src/blob/ca647cfa4ec3ccb8360714bc0ebc32a394f7fb6a/sys/arch/amd64/isa/clock.c#L142

mc146818_write
https://github.com/openbsd/src/blob/ca647cfa4ec3ccb8360714bc0ebc32a394f7fb6a/sys/arch/amd64/isa/clock.c#L150

Registers constant
https://github.com/openbsd/src/blob/ca647cfa4ec3ccb8360714bc0ebc32a394f7fb6a/sys/dev/ic/mc146818reg.h#L65-L112

outb
https://github.com/openbsd/src/blob/ca647cfa4ec3ccb8360714bc0ebc32a394f7fb6a/sys/arch/amd64/include/pio.h#L147

inb
https://github.com/openbsd/src/blob/ca647cfa4ec3ccb8360714bc0ebc32a394f7fb6a/sys/arch/amd64/include/pio.h#L57

How was this PR tested?

Notes for reviewers

[ytakano]

Just curiosity, why did you implement this driver?

[Koichi98]

Just curiosity, why did you implement this driver?

Since we need time management system for handling things like access times in the file system. While this may seem redundant once NTP is implemented, it's still good to have a reliable time source to fall back on if NTP synchronization fails. Also, another reason is to build a time management framework into Awkernel now, which will make future integration with NTP much smoother.