drivers: wifi: eswifi: Drop WIFI_ESWIFI_NAME config

The WIFI_ESWIFI_NAME config would be uselful when there is no device
tree alternative.  The esWIFI driver already is on device tree and the
label property exists.  This remove WIFI_ESWIFI_NAME Kconfig variable
and switch to device tree equivalent.

Signed-off-by: Gerson Fernando Budke <gerson.budke@atl-electronics.com>