fix: correct the check for MbedTLS makefile

This patch addresses an issue introduced in a previous
commit where the inclusion of the MbedTLS makefile was
incorrect.

Change-Id: Icdae1d85e4bc5663f68b12a9087084ce667f38f4
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
1 file changed