[SPARC]: beautify vmlinux.lds

Make vmlinux.lds almost readable.
When going through the file fixed the following:
- Use PAGE_SIZE as replacement for hardcoded 4096
- Moves label definitions inside {} to avoid ld alignment
  that may be added between label and section

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>