arm: mvebu: Replace hardcoded values 0x0030/0x4030 by proper calculation

These hardcoded values were calculated from CONFIG_SPL_TEXT_BASE macro. Now
this macro is configurable via Kconfig, so calculate values 0x0030/0x4030
at compile time via CONFIG_SPL_TEXT_BASE option. Values 0x0030/0x4030
represents offset of CONFIG_SPL_TEXT_BASE from address 0x40000000.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>