[POWERPC] 85xx: Drop use of SYNC macro in head_fsl_booke.S

Eliminate needless invocation of the SYNC macro (which always evaluates to
nothing on BookE) from head_fsl_booke.S (for both arch/ppc & arch/powerpc).

Signed-off-by: Becky Bruce <becky.bruce@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>