intel/dump_gpu: fix --platform option

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/2201>
diff --git a/src/intel/tools/intel_dump_gpu.in b/src/intel/tools/intel_dump_gpu.in
index 3efa0d4..0395af0 100755
--- a/src/intel/tools/intel_dump_gpu.in
+++ b/src/intel/tools/intel_dump_gpu.in
@@ -82,7 +82,7 @@
             shift
             ;;
         --platform=*)
-            platform=${1##-p}
+            platform=${1##--platform=}
             add_arg "platform=${platform}"
             shift
             ;;