qtbase: typo about virtual/egl depends

The proper 'virtual' name for EGL is virtual/egl, not virtual/libegl,
as per meta/recipes-graphics/mesa/mesa-common.inc.

Signed-off-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>