ARM: mach-h720x: convert boot_params to atag_offset

The value used for boot_params in h7201-eval.c is nonsensical, given that
PLAT_PHYS_OFFSET is defined to 0x40000000.  Left unchanged to purposely
break the build to get its maintainer's attention.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>