spi: Switch to signed types for *_native_cs SPI controller fields

stable inclusion
from stable-5.10.63
commit ded9137fcf0d729dbe65aa98c411352f40b22970
bugzilla: 182231 https://gitee.com/openeuler/kernel/issues/I4EFS1

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ded9137fcf0d729dbe65aa98c411352f40b22970

--------------------------------

commit 35f3f850 upstream.

While fixing undefined behaviour the commit f60d7270 ("spi: Avoid
undefined behaviour when counting unused native CSs") missed the case
when all CSs are GPIOs and thus unused_native_cs will be evaluated to
-1 in unsigned representation. This will falsely trigger a condition
in the spi_get_gpio_descs().

Switch to signed types for *_native_cs SPI controller fields to fix above.

Fixes: f60d7270 ("spi: Avoid undefined behaviour when counting unused native CSs")
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210510131242.49455-1-andriy.shevchenko@linux.intel.comSigned-off-by: NMark Brown <broonie@kernel.org>
Signed-off-by: NNobuhiro Iwamatsu (CIP) <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

include/linux/spi/spi.h

@@ -646,8 +646,8 @@ struct spi_controller {
 	int			*cs_gpios;
 	struct gpio_desc	**cs_gpiods;
 	bool			use_gpio_descriptors;
-	u8			unused_native_cs;
-	u8			max_native_cs;
+	s8			unused_native_cs;
+	s8			max_native_cs;
 
 	/* statistics */
 	struct spi_statistics	statistics;