i965: Switch BRW_NEW_CURBE_OFFSETS to BRW_NEW_PUSH_CONSTANT_ALLOCATION.

i965: Switch BRW_NEW_CURBE_OFFSETS to BRW_NEW_PUSH_CONSTANT_ALLOCATION.

The BRW_NEW_CURBE_OFFSETS dirty bit is signalled when changing the
partitioning of the Constant Buffer URB section between the various
shader stages, on Gen4-5.

BRW_NEW_PUSH_CONSTANT_ALLOCATION is basically the same thing on Gen7+.

So, save a bit, and use the new name.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>