m68k: Use new printk() extension %pS to print symbols

This changes the oops and backtrace code to use the new `%pS' printk()
extension to print out symbols rather than manually calling print_symbol.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>