e300: increase CONFIG_SYS_BOOTMAPSZ to allow booting large kernels

e300: increase CONFIG_SYS_BOOTMAPSZ to allow booting large kernels

Newer Linux kernels can overrun the initial memory window used for
booting with their BSS area. When this happens, they overwrite the FDT
and silently fail to boot.

On e300 CPUs, the Linux kernel uses an initial BAT covering the first
256MB of RAM. See arch/powerpc/kernel/head_32.S for details. Increase
the value of CONFIG_SYS_BOOTMAPSZ to accommodate the maximum value
allowed by Linux. This will allow very large kernels to boot.

Signed-off-by: Ira W. Snyder <iws@ovro.caltech.edu>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>