Revert "gallium: Force blend color to 16-byte alignment"

This reverts commit d8d6091a84.

Heap allocations may be only 8-byte aligned on 32-bit system, and so having
members with 16-byte alignment (such as in the case where pipe_blend_color is
embedded in radeonsi's si_context) is undefined behavior which indeed causes
crashes when compiled with gcc -O3.

Cc: <mesa-stable@lists.freedesktop.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96835
Signed-off-by: Tim Rowley <timothy.o.rowley@intel.com>
Acked-by: Chuck Atkins <chuck.atkins@kitware.com>

src/gallium/include/pipe/p_state.h

@@ -326,17 +326,7 @@ struct pipe_blend_state
 
 struct pipe_blend_color
 {
-   /**
-    * Making the color array explicitly 16-byte aligned provides a hint to
-    * compilers to make more efficient auto-vectorization optimizations.
-    * The actual performance gains from vectorizing the blend color array are
-    * fairly minimal, if any, but the alignment is necessary to work around
-    * buggy vectorization in some compilers which fail to generate the correct
-    * unaligned accessors resulting in a segfault.  Specifically several
-    * versions of the Intel compiler are known to be affected but it's likely
-    * others are as well.
-    */
-   PIPE_ALIGN_VAR(16) float color[4];
+   float color[4];
 };