arm/ftrace: fix ftrace_return_addr() to ftrace_return_address()

The clean up of CALLER_ADDR*() functions required the archs to either
use the default __builtin_return_address(X) (where X > 0) or override
it with something the arch can use. To override it, the arch would
define ftrace_return_address(x).

The arm architecture requires this to be redefined but instead of
defining ftrace_return_address(x) it defined ftrace_return_addr(x).

Fixes: eed542d6

 (ftrace: Make CALLER_ADDRx macros more generic)
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>