radeon/vcn: add encode header algorithms

radeon/vcn: add encode header algorithms

Since bitstream headers, e.g. sps, pps, slice, are encoded in driver side, we
need to add corresponding algorithms that required to generate those headers.
According to h.264 specs, signed/unsigned interger Exp-Golomb-coded syntax
element with left bit first (code_se and code_ue) and unsigned integer using
n bits (code_fixed_bits) descriptors function are needed. Therefore, adding
those algorithms and related variables and output algorithms here.

Signed-off-by: Boyuan Zhang <boyuan.zhang@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>