fix(arm_fpga): remove explicit cross compiler line from CI script

We already define a (cross) compiler centrally (in common_def.sh), so
there is no need to explicitly set one for the Arm FPGA.

Change-Id: Ie861e1330aab97871e5b6a737b7031ddf1ee829b
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/script/tf-coverity/tf-cov-make b/script/tf-coverity/tf-cov-make
index 7fb0609..79a42ff 100755
--- a/script/tf-coverity/tf-cov-make
+++ b/script/tf-coverity/tf-cov-make
@@ -256,7 +256,7 @@
 #
 # Arm internal FPGA port
 #
-make PLAT=arm_fpga $(common_flags) CROSS_COMPILE=aarch64-none-elf- \
+make PLAT=arm_fpga $(common_flags) \
     FPGA_PRELOADED_DTB_BASE=0x88000000 PRELOADED_BL33_BASE=0x82080000 all
 
 #