sparc: Fix build with DEBUG_PAGEALLOC enabled.

arch/sparc/mm/init_64.c:1622:22: error: unused variable '__swapper_4m_tsb_phys_patch_end' [-Werror=unused-variable]
arch/sparc/mm/init_64.c:1621:22: error: unused variable '__swapper_4m_tsb_phys_patch' [-Werror=unused-variable]

Signed-off-by: David S. Miller <davem@davemloft.net>