powerpc/perf: remove current_is_64bit()

Since commit ed1cd6d ("powerpc: Activate CONFIG_THREAD_INFO_IN_TASK")
current_is_64bit() is quivalent to !is_32bit_task().
Remove the redundant function.

Link: linuxppc/issues#275
Link: https://lkml.org/lkml/2019/9/12/540

Fixes: linuxppc#275
Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michal Suchanek <msuchanek@suse.de>

arch/powerpc/perf/callchain.c

@@ -284,16 +284,6 @@ static void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
 	}
 }
 
-static inline int current_is_64bit(void)
-{
-	/*
-	 * We can't use test_thread_flag() here because we may be on an
-	 * interrupt stack, and the thread flags don't get copied over
-	 * from the thread_info on the main stack to the interrupt stack.
-	 */
-	return !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
-}
-
 #else  /* CONFIG_PPC64 */
 /*
  * On 32-bit we just access the address and let hash_page create a
@@ -321,11 +311,6 @@ static inline void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry
 {
 }
 
-static inline int current_is_64bit(void)
-{
-	return 0;
-}
-
 static inline int valid_user_sp(unsigned long sp, int is_64)
 {
 	if (!sp || (sp & 7) || sp > TASK_SIZE - 32)
@@ -486,7 +471,7 @@ static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
 void
 perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
-	if (current_is_64bit())
+	if (!is_32bit_task())
 		perf_callchain_user_64(entry, regs);
 	else
 		perf_callchain_user_32(entry, regs);