ASoC: wcd-mbhc: Increase number of measurements for impedance calc to 900

Stereo headset sometimes gets detected as mono headset.
This is due to incomplete ramp on headphone left and/or right.
Increase the retry loop counter to 900 so as to give
more time for the ramp to be completed.

CRs-Fixed: 2084750
Change-Id: I38f9b07e2063e2298a2e9b8a1c79b7b1283484ae
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>