egt-samples-contribution_1.1.bb: Inherit from missing siteinfo class

Since we use SITEINFO_ENDIANNESS this class is required or else this
recipe will be parsed but wont find libegl and fail with errors like

ERROR: Nothing PROVIDES 'libegt' (but /mnt/jenkins/workspace/yocto-world-glibc/sources/meta-atmel/recipes-egt/apps/egt-samples-contribution_1.1.bb DEPENDS on or otherwise requires it)
libegt was skipped: Requires little-endian target.
libegt was skipped: Requires little-endian target.
ERROR: Nothing RPROVIDES 'egt-samples-contribution' (but /mnt/jenkins/workspace/yocto-world-glibc/sources/meta-atmel/recipes-egt/apps/egt-samples-contribution_1.1.bb RDEPENDS on or otherwise requires it)
No eligible RPROVIDERs exist for 'egt-samples-contribution'
NOTE: Runtime target 'egt-samples-contribution' is unbuildable, removing...
Missing or unbuildable dependency chain was: ['egt-samples-contribution']

Signed-off-by: Khem Raj <raj.khem@gmail.com>

recipes-egt/apps/egt-samples-contribution_1.1.bb

@@ -18,7 +18,7 @@ S = "${WORKDIR}/git"
 
 EXTRA_OECMAKE += "-DEGT_SAMPLES_CONTRIBUTION_SLIDERB=true"
 
-inherit pkgconfig cmake
+inherit pkgconfig cmake siteinfo
 
 python __anonymous () {
     endianness = d.getVar('SITEINFO_ENDIANNESS')