swr: set PIPE_CAP_MAX_VARYINGS correctly

Unfortunately swr was missed in the original commit. The number of
varyings should generally match up to what's reported as the shader
caps for fragment inputs.

Fixes: 6010d7b8e8 (gallium: add PIPE_CAP_MAX_VARYINGS)
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Alok Hota <alok.hota@intel.com>
Cc: 19.0 <mesa-stable@lists.freedesktop.org>
(cherry picked from commit 8c859367df)

src/gallium/drivers/swr/swr_screen.cpp

@@ -369,6 +369,8 @@ swr_get_param(struct pipe_screen *screen, enum pipe_cap param)
       return 32;
    case PIPE_CAP_MAX_SHADER_BUFFER_SIZE:
       return 1 << 27;
+   case PIPE_CAP_MAX_VARYINGS:
+      return 32;
 
    case PIPE_CAP_VENDOR_ID:
       return 0xFFFFFFFF;