soc: xilinx: xlnx_vcu: Depends on HAS_IOMEM for xlnx_vcu

xlnx_vcu driver uses devm_ioremap_nocache, which is included
only when HAS_IOMEM is enabled.

drivers/soc/xilinx/xlnx_vcu.o: In function `xvcu_probe':
   xlnx_vcu.c:(.text+0x116): undefined reference to `devm_ioremap_nocache'
   xlnx_vcu.c:(.text+0x1ae): undefined reference to `devm_ioremap_nocache'

Signed-off-by: Dhaval Shah <dshah@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>