sh: fix function signature of cpu_coregroup_mask to match pointer type

The signedness mismatch of the argument type produces an error
compiling kernel/sched/core.c with -Werror=incompatible-pointer-types,
which is now used by default.

Fixes: ea8daa7b97 "kbuild: Add option to turn incompatible pointer check into error"
Signed-off-by: Rich Felker <dalias@libc.org>

arch/sh/include/asm/topology.h

@@ -17,7 +17,7 @@
 
 #define mc_capable()    (1)
 
-const struct cpumask *cpu_coregroup_mask(unsigned int cpu);
+const struct cpumask *cpu_coregroup_mask(int cpu);
 
 extern cpumask_t cpu_core_map[NR_CPUS];