feat(sgi): remove override for `ARM_BL31_IN_DRAM` build-option

RD-N2* variants of Neoverse reference design platforms could be
configured to boot from SRAM or DRAM. Having ARM_BL31_IN_DRAM set to 1
within the common makefile would deter these platforms from having this
flexibility. Remove the default override configuration for

Signed-off-by: Rohit Mathew <rohit.mathew@arm.com>
Change-Id: I8d79969c003a984675cbe705de890b51a1f7f4ea
1 file changed