powerpc/kprobes: Fixes for kprobe_lookup_name() on BE

Fix two issues with kprobes.h on BE which were exposed with the
optprobes work:
  - one, having to do with a missing include for linux/module.h for
    MODULE_NAME_LEN -- this didn't show up previously since the only
    users of kprobe_lookup_name were in kprobes.c, which included
    linux/module.h through other headers, and
  - two, with a missing const qualifier for a local variable which ends
    up referring a string literal. Again, this is unique to how
    kprobe_lookup_name is being invoked in optprobes.c

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/kprobes.h

@@ -29,6 +29,7 @@
 #include <linux/types.h>
 #include <linux/ptrace.h>
 #include <linux/percpu.h>
+#include <linux/module.h>
 #include <asm/probes.h>
 #include <asm/code-patching.h>
 
@@ -61,7 +62,7 @@ typedef ppc_opcode_t kprobe_opcode_t;
 #define kprobe_lookup_name(name, addr)					\
 {									\
 	char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];		\
-	char *modsym;							\
+	const char *modsym;							\
 	bool dot_appended = false;					\
 	if ((modsym = strchr(name, ':')) != NULL) {			\
 		modsym++;						\