riscv: ensure cpu_ops_sbi is declared

Sparse complains that cpu_ops_sbi is used undeclared:
arch/riscv/kernel/cpu_ops_sbi.c:17:29: warning: symbol 'cpu_ops_sbi' was not declared. Should it be static?

Fix the warning by adding cpu_ops_sbi to cpu_ops_sbi.h & including that
where used.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220714080235.3853374-1-conor.dooley@microchip.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/cpu_ops_sbi.h

@@ -10,6 +10,8 @@
 #include <linux/sched.h>
 #include <linux/threads.h>
 
+extern const struct cpu_operations cpu_ops_sbi;
+
 /**
  * struct sbi_hart_boot_data - Hart specific boot used during booting and
  *			       cpu hotplug.

arch/riscv/kernel/cpu_ops.c

@@ -9,6 +9,7 @@
 #include <linux/string.h>
 #include <linux/sched.h>
 #include <asm/cpu_ops.h>
+#include <asm/cpu_ops_sbi.h>
 #include <asm/sbi.h>
 #include <asm/smp.h>