i965: Don't inline intel_batchbuffer_require_space().

i965: Don't inline intel_batchbuffer_require_space().

It's called by the inline intel_batchbuffer_begin() function which
itself is used in BEGIN_BATCH. So in sequence of code emitting multiple
packets, we have inlined this ~200 byte function multiple times. Making
it an out-of-line function presumably improved icache usage.

Improves performance of Gl32Batch7 by 3.39898% +/- 0.358674% (n=155) on
Ivybridge.

Reviewed-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>