riscv: fix build warning of missing prototypes

Add the missing header in file, it was lost in original implementation.

The warning message as follows:
 - no previous prototype for 'patch_text_nosync' [-Wmissing-prototypes]
 - no previous prototype for 'patch_text' [-Wmissing-prototypes]

Changed in v2:
 - Correct the typo of commit message.
Signed-off-by: NZong Li <zong.li@sifive.com>
Reported-by: Nkbuild test robot <lkp@intel.com>
Reviewed-by: NAtish Patra <atish.patra@wdc.com>
Signed-off-by: NPalmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/kernel/patch.c

@@ -11,6 +11,7 @@
 #include <asm/kprobes.h>
 #include <asm/cacheflush.h>
 #include <asm/fixmap.h>
+#include <asm/patch.h>
 
 struct patch_insn {
 	void *addr;