sparc32: More memory probing consolidation.

The PROM library function prom_meminit() builds a table,
prom_phys_avail[], just so that probe_memory() in
arch/sparc/mm/fault.c can copy it into sp_banks[].

Just have prom_meminit() fill in the sp_banks[] array directly, and
remove duplicated sort() function.

Signed-off-by: David S. Miller <davem@davemloft.net>