net: fill in MODULE_DESCRIPTION()s for rvu_mbox

W=1 builds now warn if module is built without a MODULE_DESCRIPTION().
Add descriptions to the Marvel RVU mbox driver.
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20240123190332.677489-11-leitao@debian.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/marvell/octeontx2/af/mbox.c

@@ -413,4 +413,5 @@ const char *otx2_mbox_id2name(u16 id)
 EXPORT_SYMBOL(otx2_mbox_id2name);
 
 MODULE_AUTHOR("Marvell.");
+MODULE_DESCRIPTION("Marvell RVU NIC Mbox helpers");
 MODULE_LICENSE("GPL v2");