powerpc/40x: Map 32Mbytes of memory at startup

powerpc/40x: Map 32Mbytes of memory at startup

[ Upstream commit 06e7cbc29e97b4713b4ea6def04ae8501a7d1a59 ]

As reported by Carlo, 16Mbytes is not enough with modern kernels
that tend to be a bit big, so map another 16M page at boot.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/89b5f974a7fa5011206682cd092e2c905530ff46.1632755552.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@kernel.org>