m68k: use jbsr to call functions instead of bsrl

There is a few places that the m68k entry code uses the bsrl instruction
to call other functions. That instruction is only supported on 68020 and
higher CPU types. If we use jbsr instead the code will be clean for all
68k and ColdFire CPU types.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>