staging: wilc1000: fix line over 80 chars in wilc_wfi_cfg_tx_vendor_spec()

Fix line over 80 characters issues reported by checkpatch.pl script in
wilc_wfi_cfg_tx_vendor_spec() by using temporary variable. Simplified
'if else' condition with 'if'.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>