r600g: reduce memory usage from range/block hash table.

r600g: reduce memory usage from range/block hash table.

This table covered a large range unnecessarily, reduce the address
range covered, use the fact that the bottom two bits aren't significant,
and remove unused fields from the range struct. It also drops the hash_size/shift in context in favour of a define, which should make doing the math
a bit less CPU intensive.

valgrind glxinfo
Before:
==320==     in use at exit: 419,754 bytes in 706 blocks
==320==   total heap usage: 3,691 allocs, 2,985 frees, 7,272,467 bytes allocated

After:
==967==     in use at exit: 419,754 bytes in 706 blocks
==967==   total heap usage: 3,552 allocs, 2,846 frees, 3,550,131 bytes allocated

Signed-off-by: Dave Airlie <airlied@redhat.com>