build: fix implicit self-provides

build: fix implicit self-provides

Fix setting implicit self-provides for packages when they don't have any
PROVIDES specified.

Remove redundant self-provide for kmods, since kmods are packages and
will have a self-provide added already.

Fixes: 5ed650a ("build: add support for virtual provides")
Fixes: 9b37b71 ("build: provide virtual self in kmods")
Signed-off-by: George Sapkin <george@sapk.in>
Link: https://github.com/openwrt/openwrt/pull/21369
(cherry picked from commit 2d844a077089575ab67fcbd15e021a981387e668)
Link: https://github.com/openwrt/openwrt/pull/21547
Signed-off-by: Robert Marko <robimarko@gmail.com>