net: nixge: fix spelling mistake in Kconfig: "Instuments" -> "Instruments"

There is a spelling mistake in the Kconfig. Fix it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20201216120020.13149-1-colin.king@canonical.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/ni/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
 #
-# National Instuments network device configuration
+# National Instruments network device configuration
 #
 
 config NET_VENDOR_NI