cnss2: Provide sysfs control for vdd-wlan-en

For qcn7605 USB, firmware download and error
recovery are handled by entities in userspace.
cnss needs to provide access vdd-wlan-en to
the kickstart userspace via sysfs

Change-Id: I53da7f2f7ebb2ec55f98fc328a550181dccb5a18
Signed-off-by: Rajasekaran Kalidoss <rkalidos@codeaurora.org>