MIPS: dma-noncoherent: Remove bogus condition in dma_sync_phys()

Commit e36863a5 ("MIPS: HIGHMEM DMA on noncoherent MIPS32
processors") introduced code which:

  1) Calculates an offset within a page, by ANDing an address
     with ~PAGE_MASK.

  2) Checks whether that offset is >= PAGE_SIZE.

This check can never evaluate true, making the code it guards
unreachable. smatch spots bogus arithmetic resulting from the
impossible condition, resulting in the following warning:

  arch/mips/mm/dma-noncoherent.c:125
    dma_sync_phys() warn: mask and shift to zero

Fix this by removing the impossible to satisfy condition & the
unreachable code it guards.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: Christoph Hellwig <hch@lst.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>

arch/mips/mm/dma-noncoherent.c

@@ -120,13 +120,8 @@ static inline void dma_sync_phys(phys_addr_t paddr, size_t size,
 		if (PageHighMem(page)) {
 			void *addr;
 
-			if (offset + len > PAGE_SIZE) {
-				if (offset >= PAGE_SIZE) {
-					page += offset >> PAGE_SHIFT;
-					offset &= ~PAGE_MASK;
-				}
+			if (offset + len > PAGE_SIZE)
 				len = PAGE_SIZE - offset;
-			}
 
 			addr = kmap_atomic(page);
 			dma_sync_virt(addr + offset, len, dir);