xen/arm: introduce allocate_static_memory

xen/arm: introduce allocate_static_memory

This commit introduces a new function allocate_static_memory to allocate
static memory as guest RAM for domains on Static Allocation.

It uses acquire_domstatic_pages to acquire pre-configured static memory
for the domain, and uses guest_physmap_add_pages to set up the P2M table.
These pre-defined static memory banks shall be mapped to the usual guest
memory addresses (GUEST_RAM0_BASE, GUEST_RAM1_BASE) defined by
xen/include/public/arch-arm.h.

In order to deal with the trouble of count-to-order conversion when page number
is not in a power-of-two, this commit exports p2m_insert_mapping and introduce
a new function guest_physmap_add_pages to cope with adding guest RAM p2m
mapping with nr_pages.

Signed-off-by: Penny Zheng <penny.zheng@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>