libcacard: list oslib-obj-y file explicitly
libcacard: list oslib-obj-y file explicitly

We will grow the list of files in the next patches, but libcacard
should remain slim.

Signed-off-by: Paolo Bonzini <69d3ebcf5ee4e7f05a50dc23cd96655b730804b4@redhat.com>

elmarco/libcacard,SPICE/libcacard,SPICE/libcacard,elmarco/libcacard