perf tools: Get rid of map_groups__fixup_end()

The map_groups__fixup_end() was called to set end addresses of kernel
map and module maps.  But now machine__create_modules() is set the end
address of modules properly so the only remaining piece is the kernel
map.  We can set it with adjacent module's address directly instead of
calling the map_groups__fixup_end().

Signed-off-by: Namhyung Kim <namhyung@kernel.org>