support/kconfig: Fix remaining 'kernel' mention

This patch update the patch for kernel's kconfig to add remaining
'kernel' mention.
It also applies this patch to buildroot's kconfig.

Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>