i965/fs: Fix INTEL_DEBUG=perf program key printing.

i965/fs: Fix INTEL_DEBUG=perf program key printing.

When dumping differences in program keys, it printed messages of the
format:

   [Name of thing that changed]  [new]->[old]

This was terribly confusing: the right arrow implies "the value changed
from this to that", when in fact the message conveyed the opposite.

Except that some of the time, it didn't, since we accidentally swapped
the arguments to brw_debug_recompile_sampler_key.  With two swaps, it
would often come out in the expected format.

This patch fixes it to properly print:

   [Name of thing that changed]  [old]->[new]

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>