net: cnss: remove 3.3v PMIC gpio enable feature

PMIC gpio used for the 3.3v power supply to wlan has been
converted to rome_vreg fixed regulator. This Fixed regulator
shared by both WLAN and BT. Remove PMIC gpio enable dead code
from CNSS SDIO platform driver.

CRs-Fixed: 945575
Change-Id: Ifbb17e05969da25ec9a87844b4409e26f07fca69
Signed-off-by: Sarada Prasanna Garnayak <sgarna@codeaurora.org>