el3_payload: Remove CROSS_COMPILE default

Remove the default value of CROSS_COMPILE from EL3 Makefile
and use the user-defined value.

Change-Id: Icaed8aec0a82293dbefc579b89d0eef23c676f6a
Signed-off-by: Sathees Balya <sathees.balya@arm.com>
2 files changed