Some architectures such as ARM don't use asm-generic/iomap.h and instead
define their own implementation for ioread32 and iowrite32.
This can be checked using the CONFIG_GENERIC_IOMAP preprocessor.

The signature used inside asm-generic/io.h uses volatile for the address
parameter. Thus it is necessary to accomodate this change.

Moreover, ARM uses macros to define ioread32be and iowrite32be, so it is
necessary to define a function on top of the macro to allow for
assignation.
Note: other architectures may not use macros, or use macros for ioread32
and iowrite32, in which case this patch may not work and has to be
adapted.
Signed-off-by: Gwenhael GOAVEC <gwenhael.goavec@femto-st.fr>
Signed-off-by: Mathis MARION <mathis.marion@grenoble-inp.org>