ASoC: wcd9335: Give more headroom for headphone PA ramp

Give more headroom for headphone PA ramp up and down during
impedance detection to avoid any click and pop or ramp error.

Change-Id: I3e3980e48ce19955b4230876887adfde5b44e8ea
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>