ASoC: msm8x16-wcd: Update HPH PA gain for Tombak

HPH PA gain is configurable and same as Conga, 0dB or -4.5 dB.
And the impedance-gain mapping rule is also the same as Conga.
Update the HPH PA gain for Tombak as well.

CRs-Fixed: 958890
Change-Id: I49901ab36d39b37846c10e52c3fd5f8e0e2ae5cd
Signed-off-by: Walter Yang <yandongy@codeaurora.org>