kbuild: fix dependency generation

kbuild: fix dependency generation

Commit 2e3646e51b2d6415549b310655df63e7e0d7a080 changed the way
the split config tree is built, but failed to also adjust fixdep
accordingly - if changing a config option from or to m, files
referencing the respective CONFIG_..._MODULE (but not the
corresponding CONFIG_...) didn't get rebuilt.

The problem is that trisate symbol are represent with three
different symbols:
SYMBOL=n => no symbol defined
SYMBOL=y => CONFIG_SYMBOL defined to '1'
SYMBOL=m => CONFIG_SYMBOL_MODULE defined to '1'

But conf_split_config do not distingush between the =y and =m case,
so only the =y case is honoured.
This is fixed in fixdep so when a CONFIG symbol with
_MODULE is found we skip that part and only look
for the CONFIG_SYMBOL version.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>