serial: SERIAL_FSL_LPUART should depend on HAS_DMA

If NO_DMA=y:

drivers/built-in.o: In function `lpuart_dma_rx_free':
fsl_lpuart.c:(.text+0x7da28): undefined reference to `dma_unmap_single'
drivers/built-in.o: In function `lpuart_dma_tx_free':
fsl_lpuart.c:(.text+0x7da60): undefined reference to `dma_unmap_single'
drivers/built-in.o: In function `lpuart_dma_rx':
fsl_lpuart.c:(.text+0x7dab8): undefined reference to `dma_sync_single_for_cpu'
drivers/built-in.o: In function `lpuart_dma_tx':
fsl_lpuart.c:(.text+0x7db7e): undefined reference to `dma_sync_single_for_cpu'
drivers/built-in.o: In function `lpuart_copy_rx_to_tty':
fsl_lpuart.c:(.text+0x7dcd4): undefined reference to `dma_sync_single_for_cpu'
make[3]: *** [vmlinux] Error 1

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>