mmc: sdhci-mmc-ice: Factor out ice_cfg_start from sdhci_msm_ice_cfg

Factor out the logic of getting ice config parameters from
sdhci_msm_ice_cfg().

With ICE2.0, same sdhci_msm_ice_cfg function is being called from cmdq
and noncq. But with ICE3.0 support, cmdq needs a separate host op.
Since this logic of getting ice config is common for noncq and cmdq,
by having it in separate function, same can be reused
in cmdq host op as-well.

Change-Id: If2cf26667acd54cb7ee7bd6283d8f24fcbf60791
Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>