Add support for IYUV in vaCreateSurfaces()

Add support for IYUV in vaCreateSurfaces()

Actually IYUV is indentical to I420. This fixes the failue reported by
CreateSurfacesTest.SupportedPixelFormats in gtest

before:

[  FAILED  ] CreateSurfacesTest.SupportedPixelFormats (0 ms)
[----------] 1 test from CreateSurfacesTest (0 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (2 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] CreateSurfacesTest.SupportedPixelFormats

after:

[----------] 1 test from CreateSurfacesTest
[ RUN      ] CreateSurfacesTest.SupportedPixelFormats
[       OK ] CreateSurfacesTest.SupportedPixelFormats (1 ms)
[----------] 1 test from CreateSurfacesTest (1 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (4 ms total)
[  PASSED  ] 1 test.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98033
Tested-by: Eoff, Ullysses A <ullysses.a.eoff@intel.com>
Signed-off-by: Xiang, Haihao <haihao.xiang@intel.com>
Reviewed-by: Eoff, Ullysses A <ullysses.a.eoff@intel.com>