net: fill in MODULE_DESCRIPTION()s for Qualcom drivers

W=1 builds now warn if module is built without a MODULE_DESCRIPTION().
Add descriptions to the Qualcom rmnet and emac drivers.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Subash Abhinov Kasiviswanathan <quic_subashab@quicinc.com>
Signed-off-by: David S. Miller <davem@davemloft.net>