Bluetooth: HFP_AG: Optimize feature access

Add `BOTH_SUPT_FEAT(ag, _hf_feature, _ag_feature)` to check if the
feature is supported by both side.
Add `HF_SUPT_FEAT(ag, _feature)` to check if the feature is supported
by HF.
Add `AG_SUPT_FEAT(ag, _feature)` to check if the feature is supported
by AG.

Use `BOTH_SUPT_FEAT/HF_SUPT_FEAT/AG_SUPT_FEAT` to optimize code that
checks whether a feature is supported.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>