vulkan: Fix incompatible type build warning
Make declare/define a function consistent. Note that GstBaseTransform::set_caps should return gboolean
Compiling C object subprojects/gst-plugins-bad/ext/vulkan/f3f9d6b@@gstvulkan@sha/vkviewconvert.c.obj.
../subprojects/gst-plugins-bad/ext/vulkan/vkviewconvert.c(644):
warning C4133: '=': incompatible types - from 'GstFlowReturn (__cdecl *)(GstBaseTransform *,GstCaps *,GstCaps *)'
to 'gboolean (__cdecl *)(GstBaseTransform *,GstCaps *,GstCaps *)'
Edited by Seungha Yang