arm: mach-k3: common: Use ddr_init in spl_enable_dcache

arm: mach-k3: common: Use ddr_init in spl_enable_dcache

The spl_enable_dcache() function calls dram_init_banksize()
to get the total memory size. Normally the dram_init_banksize()
setups the memory banks, while the total size is reported
by ddr_init(). This worked so far for K3 since we set the
gd->ram_size in dram_init_banksize() as well.

Signed-off-by: Georgi Vlaev <g-vlaev@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>