kbuild: fix ia64 breakage after introducing make -rR

kbuild used $¤(*F to get filename of target without extension.
This was used in several places all over kbuild, but introducing
make -rR broke his for all cases where we specified full path to
target/prerequsite. It is assumed that make -rR disables old style
suffix-rules which is why is suddenly failed.

ia64 was impacted by this change because several div* routines in
arch/ia64/lib are build using explicit paths and then kbuild failed.

Thanks to David Mosberger-Tang <David.Mosberger@acm.org> for an explanation
what was the root-cause and for testing on ia64.

This patch also fixes two uses of $(*F) in arch/um

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/Makefile.modpost

@@ -72,7 +72,7 @@ $(modules:.ko=.mod.c): __modpost ;
 # Step 5), compile all *.mod.c files
 
 # modname is set to make c_flags define KBUILD_MODNAME
-modname = $(*F)
+modname = $(notdir $(@:.mod.o=))
 
 quiet_cmd_cc_o_c = CC      $@
       cmd_cc_o_c = $(CC) $(c_flags) $(CFLAGS_MODULE)	\