ASoC: rt1011: fix warning reported by kbuild test robot and minor issue

This patch fixes following issues:
- warning: this decimal constant is unsigned only in ISO C90
- sparse: incorrect type in assignment
- check if value.integer.value is zero for "R0 Load Mode" control

Signed-off-by: Shuming Fan <shumingf@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>