drm/amd/display: Rename bytes_pp to the correct bits_pp

[Why]
Struct dcn_dsc_state is used for reading current state
and parameters of DSC on a pipe, the target rate parameter
uses bytes per pixel even though its reading BITS_PER_PIXEL
register.

[How]
Changing it to Bits Per Pixel for consistency.

Signed-off-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Reviewed-by: Mikita Lipski <Mikita.Lipski@amd.com>
Acked-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>