meson.build: Move dependency addition out from if block
meson.build: Move dependency addition out from if block

The dependency object is empty when not found.  So, we can
unconditionally append it to csp_deps.

Signed-off-by: Yasushi SHOJI <afa9ca3be149447780c2f7b524d61ed3d3db63f9@spacecubics.com>

libcsp/libcsp,libcsp/libcsp