amdgpu/pm: Implement new API function "emit" that accepts buffer base and write offset

amdgpu/pm: Implement new API function "emit" that accepts buffer base and write offset

   (v3)
     Rewrote patchset to order patches as (API, hw impl, usecase)

     - added API for new power management function emit_clk_levels
       This function should duplicate the functionality of print_clk_levels,
       but this solution passes the buffer base and write offset down the stack.
     - new powerplay function emit_clock_levels, implemented by smu_emit_ppclk_levels()
       This function parallels the implementation of smu_print_ppclk_levels and
       calls emit_clk_levels, and allows the returns of errors
     - new helper function smu_convert_to_smuclk called by smu_print_ppclk_levels and
       smu_emit_ppclk_levels

Signed-off-by: Darren Powell <darren.powell@amd.com>
Reviewed-By: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>