misc: sram: partition base address belongs to __iomem space

The change fixes a warning found by sparse:

  drivers/misc/sram.c:134:20: warning: incorrect type in assignment (different address spaces)
  drivers/misc/sram.c:134:20:    expected void *base
  drivers/misc/sram.c:134:20:    got void [noderef] <asn:2>*

Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>