i2c: sh_mobile: I2C_SH_MOBILE should depend on HAS_DMA

i2c: sh_mobile: I2C_SH_MOBILE should depend on HAS_DMA

If NO_DMA=y:

drivers/built-in.o: In function `sh_mobile_i2c_dma_unmap':
i2c-sh_mobile.c:(.text+0x60de42): undefined reference to `dma_unmap_single'
drivers/built-in.o: In function `sh_mobile_i2c_xfer_dma':
i2c-sh_mobile.c:(.text+0x60df22): undefined reference to `dma_map_single'
i2c-sh_mobile.c:(.text+0x60df2e): undefined reference to `dma_mapping_error'

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>