arm: lib: Fix makefile issue

Fix the typo introduced by commit
fb7051a183cba3925f1f00c9bdadc2adcc682020.

Change-Id: Ia23c80f903ed431e60e4ba17c9c6d527e6febd87
Signed-off-by: Hong-Mei Li <a21834@motorola.com>
Reviewed-on: http://gerrit.pcs.mot.com/527915
SLT-Approved: Gerrit Code Review <gerrit-blurdev@motorola.com>
Tested-by: Jira Key <jirakey@motorola.com>
Reviewed-by: Christopher Fries <qcf001@motorola.com>
Submit-Approved: Jira Key <jirakey@motorola.com>