libfdt: Ensure INT_MAX is defined in libfdt_env.h

[ Upstream commit 53dd9dce6979bc54d64a3a09a2fb20187a025be7 ]

The next update of libfdt has a new dependency on INT_MAX. Update the
instances of libfdt_env.h in the kernel to either include the necessary
header with the definition or define it locally.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>