freedreno/regs: Define usage for all a6xx/a7xx regs

freedreno/regs: Define usage for all a6xx/a7xx regs

Could be used for knowing which regs to stomp and to verify that
only appropriate regs are emitted.

Each register that is actually being used by driver should have "usage"
defined, currently there are following usages:
- "cmd" - the register is used outside of renderpass and blits,
		roughly corresponds to registers used in ib1 for Freedreno
- "rp_blit" - the register is used inside renderpass or blits
		(ib2 for Freedreno)

It is expected that register with "cmd" usage may be written into only at
the start of the command buffer (ib1), while "rp_blit" usage indicates that
register is either overwritten by renderpass/blit (ib2) or not used if not
overwritten by a particular renderpass/blit.

Signed-off-by: Danylo Piliaiev <dpiliaiev@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23881>