Remove label-check from merge_group

It seems that the action used to check forbidden labels only works for PRs. Removing it from merge_group.

Check CHANGELOG.md on PRs to master

Implement r0 crate in assembly

This implements the `r0::init_data` and `r0::zero_bss` routines in
assembly. There is a generic implementation for `riscv32` and
`riscv64`, since `riscv64` deals with alignment problems. The routines
are kept at their old calling site so that only one hardware thread
calls them. Consequently they are also inlined into the `start_rust`
function.

[Issue #122]

Added GH action to check clippy

Add feature single-hart

Signed-off-by: Chien Wong <m@xv97.com>

Use inline assembly instead of pre-compiled blobs

Fix oor branch via linking

Temporary fix for OOR branch

Move towards GHMQ