xen/x86: free_p2m_page: use memblock_free_ptr() to free a virtual pointer

xen/x86: free_p2m_page: use memblock_free_ptr() to free a virtual pointer

free_p2m_page() wrongly passes a virtual pointer to memblock_free() that
treats it as a physical address.

Call memblock_free_ptr() instead that gets a virtual address to free the
memory.

Link: https://lkml.kernel.org/r/20210930185031.18648-3-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Shahab Vahedi <Shahab.Vahedi@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>