powerpc/fsl-booke: Fix compile warning

arch/powerpc/mm/fsl_booke_mmu.c: In function 'adjust_total_lowmem':
arch/powerpc/mm/fsl_booke_mmu.c:221: warning: format '%ld' expects type 'long int', but argument 3 has type 'phys_addr_t'

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>