sparc: unify sections.h

While doing this use standard names for start/end
so we could use definitions straight from asm-generic
for all the typical symbols.

This also allowed us to drop the use of PROVIDE in the linker
script so sprc is less non-standard on this area.

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