meson: fix some defines misspelled errors in meson.build

Defines
- HAVE_FUNC_ATTRIBUTE_RETURNS_NONNULL
- HAVE_FUNC_ATTRIBUTE_VISIBILITY
were misspelled.

Signed-off-by: Marc Dietrich <marvin24@gmx.de>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
1 file changed