wil6210: reset flow update

If card reset with firmware download executed, followed by reset
with use of firmware from build in flash, firmware download indication
remains in the hardware register.
When running firmware download flow,
the SW download indication is written by the driver to bit 0 in usage_6:
wil_fw_load(), "S(RGF_USER_USAGE_6, 1);"
This register, like all USER RGF, wasn't reset in SW reset flow.
Therefore the driver must clear it on SW reset flow.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>