usb: phy: qusb: Fix DP/DM pulsing sequence

Current DP and DM pulsing sequeunce is updating pullup on DM and DP
which is not needed. Also make sure to use VDM_SRC_EN or VDP_SRC_EN
when 0.6v is required on DM and DP respectively.

Current code is not clearing QC1 and QC2 registers when DP_DM_DPF_DMF
is invoked when rm_pulldown is set. Hence allow clearing of QC1 and QC2
registers as part of DP_DM_DPF_DMF property multiple time although
rm_pulldown is set.

Change-Id: Ib1d57a021b1e19d0a3bc691e64bf024929205df8
Signed-off-by: Mayank Rana <mrana@codeaurora.org>