arm64: ftrace: Update stale comment

In commit:

  26299b3f ("ftrace: arm64: move from REGS to ARGS")

... we folded ftrace_regs_entry into ftrace_caller, and
ftrace_regs_entry no longer exists.

Update the comment accordingly.

There should be no functional change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230123134603.1064407-8-mark.rutland@arm.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/ftrace.c

@@ -209,7 +209,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
  * | NOP      | MOV X9, LR | MOV X9, LR |
  * | NOP      | NOP        | BL <entry> |
  *
- * The LR value will be recovered by ftrace_regs_entry, and restored into LR
+ * The LR value will be recovered by ftrace_caller, and restored into LR
  * before returning to the regular function prologue. When a function is not
  * being traced, the MOV is not harmful given x9 is not live per the AAPCS.
  *