wcnss: remove the wcn external gpio configuration support

The wcn external gpio configuration has moved to WLAN firmware
code. To avoid the gpio resource request conflict and power offload
failure between wcnss platform driver and WLAN firmware.
Remove external gpio configuration from the wcnss platform driver.

Change-Id: Iaef979437d9e48d66a5e9e2fc88bc5783fed7480
Signed-off-by: Sarada Prasanna Garnayak <sgarna@codeaurora.org>