v3dv: add API entry points for sampler Ycbcr conversions

v3dv: add API entry points for sampler Ycbcr conversions

While this feature is optional in Vulkan 1.1 and we don't currently
expose it, the CTS still requires that the entry points exist.

From the Vulkan 1.1 spec:

   "If the VK_KHR_sampler_ycbcr_conversion extension is not supported,
    support for the samplerYcbcrConversion feature is optional."
   (...)
   "samplerYcbcrConversion specifies whether the implementation supports
    sampler YCBCR conversion. If samplerYcbcrConversion is VK_FALSE,
    sampler YCBCR conversion is not supported, and samplers using sampler
    YCBCR conversion must not be used."

Fixes (with Vulkan 1.1 exposed):
dEQP-VK.api.version_check.entry_points

Reviewed-by: Juan A. Suarez <jasuarez@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12338>