arm: imx8ulp: Enable full L2 cache in SPL

arm: imx8ulp: Enable full L2 cache in SPL

SRAM2 is half L2 cache and default to SRAM after system boot.
To enable the full l2 cache (512KB), it needs to reset A35 to make
the change happen.

So re-implement the jump entry function in SPL:
1. configure the core0 reset vector to entry (ATF)
2. enable the L2 full cache
3. reset A35
So when core0 up, it runs into ATF. And we have 512KB L2 cache working.

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>