MLK-14282: 4.9 rebase: LVDS display not working on iMX6QP SabreSD

MLK-14282: 4.9 rebase: LVDS display not working on iMX6QP SabreSD

Fix IPU2 DI(Display Interface) clocks for iMX6QP SABRESD. The upstream
version uses ldb_di0_podf and ldb_di1_podf as clock parents for ipu_di,
which fails to work on iMX6QP SABRESD. This patch fixes clock tree by:
- setting ipu_di selectors to ldb_di_div_sel in imx6q clock driver
- matching "ldb_di0", "ldb_di1" clock names with
  IMX6QDL_CLK_LDB_DI0_DIV_SEL, IMX6QDL_CLK_LDB_DI1_DIV_SEL; otherwise,
  ldb_di0_div_sel and ldb_di1_div_sel will not be recognized as LDB clk parents
  and will not drive the Display Interface.

Signed-off-by: Cristina Ciocan <cristina-mihaela.ciocan@nxp.com>