package/busybox: add comment about BR2_PACKAGE_BUSYBOX_SHOW_OTHERS

package/busybox: add comment about BR2_PACKAGE_BUSYBOX_SHOW_OTHERS

BR2_PACKAGE_BUSYBOX_SHOW_OTHERS is a bit special. When Busybox is
enabled, it is a Busybox option. When Busybox is not enabled, it is a
stand-alone option, forcibly enabled.

So we can safely 'select' it without ensuring (via a 'depends on' or
another 'select') that Busybox is enabled.

However, the name of this option does not express the fact that it is
safe to select it without checking Busybox, which can lead to a bit of
time-consuming head-scratching.

To avoid future puzzlement from an unsuspecting observer, add a a big
fat comment that this option can be selected without any dependency on
Busybox.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Cc: Romain Naour <romain.naour@openwide.fr>
Reviewed-by: Romain Naour <romain.naour@gmail.com>
[Thomas: slightly improve the wording of one of the comment.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>