staging: wilc1000: rename strHostIFpmkidAttr of union host_if_key_attr

This patch renames strHostIFpmkidAttr of union host_if_key_attr to
pmkid to avoid CamelCase naming convention.

Signed-off-by: Tony Cho <tony.cho@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>