ls1046ardb_qspi*: Enable RAMBOOT_PBL

Based on include/configs/ls1046ardb.h it seems that CONFIG_RAMBOOT_PBL
should have been enabled, but was not.  Enable and migrate the values to
Kconfig.

Cc: Mingkai Hu <mingkai.hu@nxp.com>
Cc: Rajesh Bhagat <rajesh.bhagat@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>