fvp_utils.sh: check if template presence before replacing

A template is expected to be created before calling gen_fvp_yaml
function but some tests [1] do not strictly generate the latter so
check if template is present before further function processing.

[1]
tf-l3-boot-tests-spm/fvp-spm-mm,fvp-spm-mm:fvp-tftf.cactus_mm-fip.tftf+bl32-cortexa35x4-debug

Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
Change-Id: I8d51d0f00cb14f4ddfe37ac369f209e60d238333
1 file changed