Function like macros cannot be assigned to function pointers. This patch
convert the function-like macros into object-macros, that the
precompiler will replace with the name of the final function.

With this patch this kind of code will work:

if (priv->mode_big_endian)
	priv.read = ioread32be;
else
	priv.read = ioread32;

Same approach has been taken on asm-generic/io.h
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Fixes: 99082eab spi/xilinx: Remove iowrite/ioread wrappers
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>