meta: Abort meta pbo path if readpixels need signed-unsigned conversion
meta: Abort meta pbo path if readpixels need signed-unsigned conversion

Meta pbo path for ReadPixels rely on BlitFramebuffer which doesn't support
signed to unsigned integer conversions and vice versa.

Without this patch, piglit test fbo_integer_readpixels_sint_uint fails, when
forced to use the meta pbo path.

v2: Make need_signed_unsigned_int_conversion() a static function. (Iago)
    Bump up the comment and the commit message. (Jason)

Signed-off-by: Anuj Phogat <e2026475996c48f0b97fd37e84129b3912980428@gmail.com>
Cc: <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Reviewed-by: Jason Ekstrand <b186559eaedf698788888c8a2559b4efb4db10d6@intel.com>
Reviewed-by: Iago Toral <a847aabaac44184372f6b1cd1a59aa254daaeb0b@igalia.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler