doc: add gpudev to the Doxygen index

[ upstream commit 79cd6f959ebc0886dd212dc4fb057ec2d91b2d39 ]

When introducing the library gpudev,
it has been forgotten to add a link in the API index.

Fixes: 8b8036a ("gpudev: introduce GPU device class library")

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Ferruh Yigit <ferruh.yigit@amd.com>

doc/api/doxy-api-index.md

@@ -22,6 +22,7 @@ The public API headers are grouped by topics:
   [compress](@ref rte_comp.h),
   [regexdev](@ref rte_regexdev.h),
   [dmadev](@ref rte_dmadev.h),
+  [gpudev](@ref rte_gpudev.h),
   [eventdev](@ref rte_eventdev.h),
   [event_eth_rx_adapter](@ref rte_event_eth_rx_adapter.h),
   [event_eth_tx_adapter](@ref rte_event_eth_tx_adapter.h),