util: Fix PIPE_FORMAT_R8G8B8_SRGB swizzles.

The only user of PIPE_FORMAT_R8G8B8_SRGB is mesa, which
per src/mesa/main/texstore.c interprets it as

  R8 G8 B8

and not the other way around.

src/gallium/auxiliary/util/u_format.csv

@@ -78,7 +78,7 @@ PIPE_FORMAT_L16_UNORM             , plain, 1, 1, un16,     ,     ,     , xxx1, r
 # SRGB formats
 PIPE_FORMAT_L8_SRGB               , plain, 1, 1, un8 ,     ,     ,     , xxx1, srgb 
 PIPE_FORMAT_A8L8_SRGB             , plain, 1, 1, un8 , un8 ,     ,     , xxxy, srgb 
-PIPE_FORMAT_R8G8B8_SRGB           , plain, 1, 1, un8 , un8 , un8 ,     , zyx1, srgb 
+PIPE_FORMAT_R8G8B8_SRGB           , plain, 1, 1, un8 , un8 , un8 ,     , xyz1, srgb 
 PIPE_FORMAT_R8G8B8A8_SRGB         , plain, 1, 1, un8 , un8 , un8 , un8 , wzyx, srgb
 PIPE_FORMAT_R8G8B8X8_SRGB         , plain, 1, 1, un8 , un8 , un8 , un8 , wzy1, srgb
 PIPE_FORMAT_A8R8G8B8_SRGB         , plain, 1, 1, un8 , un8 , un8 , un8 , zyxw, srgb