ath10k: Remove voltage regulator votes during wifi disable

When the wlan is disabled, i.e when all the interfaces are
deleted, voltage regulator votes are not removed. This leads
to more power consumption even when wlan is disabled.

Move the adding/removing of voltage regulator votes as part
of hif power on/off in SNOC targets, so that these voltage
regulator votes are there only when wlan is enabled.

Tested-on: WCN3990 hw1.0 SNOC WLAN.HL.3.1-01040-QCAHLSWMTPLZ-1

Signed-off-by: Rakesh Pillai <pillair@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1607713230-18382-1-git-send-email-pillair@codeaurora.org