tests/gem_pwrite_snooped: Fix use of GCC pragmas
tests/gem_pwrite_snooped: Fix use of GCC pragmas

Apparently GCC treats the #pragma directive as a code block and so we
returned unconditionally from memchr_inv() on the first byte fubaring
the test.

commit b04691b3e8e62bd105f0f4d8d3b9e7da187f0c90
Author: Thomas Wood <thomas.wood@intel.com>
Date:   Tue Sep 8 11:16:46 2015 +0100

    tests/gem_pwrite_snooped: disable const cast warning

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92227
Signed-off-by: Chris Wilson <711c73f64afdce07b7e38039a96d2224209e9a6c@chris-wilson.co.uk>

mv0/intel-gpu-tools,mv0/intel-gpu-tools,tiagovignatti/intel-gpu-tools,mv0/intel-gpu-tools,chenxianqin/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,mv0/intel-gpu-tools,chenxianqin/intel-gpu-tools,chenxianqin/intel-gpu-tools,tiagovignatti/intel-gpu-tools,chenxianqin/intel-gpu-tools