This patch makes paging_init() use highend_pfn/highstart_pfn globals.

It removes the need of 'high' local which was needed only by HIGHMEM config.

More important perhaps, it fixes a bug when HIGHMEM is set but there's
actually no physical highmem (highend_pfn = 0)
Signed-off-by: NFranck Bui-Huu <fbuihuu@gmail.com>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>