powerpc/prom: fix early DEBUG messages

powerpc/prom: fix early DEBUG messages

BugLink: https://bugs.launchpad.net/bugs/1855787
[ Upstream commit b18f0ae92b0a1db565c3e505fa87b6971ad3b641 ]

This patch fixes early DEBUG messages in prom.c:
- Use %px instead of %p to see the addresses
- Cast memblock_phys_mem_size() with (unsigned long long) to
avoid build failure when phys_addr_t is not 64 bits.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>