staging: et131x: et131x.c: sparse warning of incompatible types

fixed sparse warning:   incompatible types in comparison expression
			(different address spaces)

wolw and reg both are being used only for the initialization of
the __iomem area.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>