tools/check: Add explicit include path for funcs.sh.

tools/check: Add explicit include path for funcs.sh.

When the current directory is not in $PATH,
then the patch fixes the following errors:

Checking check_brctl: .: funcs.sh: not found
Checking check_crypto_lib: .: funcs.sh: not found
Checking check_curl: .: funcs.sh: not found
Checking check_iproute: .: funcs.sh: not found
Checking check_python: .: funcs.sh: not found
Checking check_python_xml: .: funcs.sh: not found
Checking check_udev: .: funcs.sh: not found
Checking check_xml2: .: funcs.sh: not found
Checking check_zlib_lib: .: funcs.sh: not found

Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>