modify acquire_domstatic_pages to take an unsigned int size parameter

modify acquire_domstatic_pages to take an unsigned int size parameter

acquire_domstatic_pages currently takes an unsigned long nr_mfns
parameter, but actually it cannot handle anything larger than an
unsigned int nr_mfns. That's because acquire_domstatic_pages is based on
assign_pages which also takes an unsigned int nr parameter.

So modify the nr_mfns parameter of acquire_domstatic_pages to be
unsigned int.

There is only one caller in
xen/arch/arm/domain_build.c:allocate_static_memory. Check that the value
to be passed to acquire_domstatic_pages is no larger than UINT_MAX. If
it is, print an error and goto fail.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>