Merge #94

94: csr: inline register reads and type conversations r=dkhayes117 a=luojia65

This pull request adds missing `#[inline]` flags on field read functions and type conversations. Field `#[inline]` marks to enable inline function optimization which speed up the code when used to build kernels and hypervisors.

Please hint me if there are more missing `#[inline]` flags in project `riscv` so I may include them in this fix too.

Off topic: would it be the time to release a 0.7.1 version now? Then we do not need to pin to commit numbers when developing risc-v projects.

r? `@Disasm`

Co-authored-by: luojia65 <me@luojia.cc>