ath10k: fix S5 power consumption issue for QCA9377

After system entering S5 (shut down but system still
providing power to QCA9377) on Ubuntu platform, power
consumption of QCA9377 is 69mA, which is too high.
The root cause is pci_soft_reset is not set for QCA9377
during pci probe.
To fix this issue, set 'pci_soft_reset' to 'th10k_pci_warm_reset',
and then the power consumption drops to a normal value(10mA).
Verified on Dell Ubuntu platform with firmware:
WLAN.TF.1.0-00002-QCATFSWPZ-5

Signed-off-by: Yu Wang <yyuwang@codeaurora.org>
Signed-off-by: Yu Wang <yyuwang@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>