rsxx: remove extraneous 'const' qualifier

The returned string from rsxx_card_state_to_str is 'const',
but the other qualifier doesn't change anything here except
causing a warning with 'clang -Wextra':

drivers/block/rsxx/core.c:393:21: warning: 'const' type qualifier on return type has no effect [-Wignored-qualifiers]
static const char * const rsxx_card_state_to_str(unsigned int state)

Fixes: f379120 ("block: IBM RamSan 70/80 trivial changes.")
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20210323215753.281668-1-arnd@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/rsxx/core.c

@@ -392,7 +392,7 @@ static irqreturn_t rsxx_isr(int irq, void *pdata)
 }
 
 /*----------------- Card Event Handler -------------------*/
-static const char * const rsxx_card_state_to_str(unsigned int state)
+static const char *rsxx_card_state_to_str(unsigned int state)
 {
 	static const char * const state_strings[] = {
 		"Unknown", "Shutdown", "Starting", "Formatting",