clk: imx6q: demote warning about pre-boot ldb_di_clk reparenting

Since 5d283b08 ("clk: imx6: Fix procedure to switch the parent
of LDB_DI_CLK"), the clock driver warns if ldb_di\d_sel is changed
from reset value on system boot. This warning is printed even if
the bootloader (or a previous kernel that did kexec) followed the
correct procedure for glitch-free reparenting.

As such systems are doing everything correctly, a warning is too
harsh. Demote to a notice, so users are still alerted, but without
cluttering a loglevel=5 boot.

While at it, add the words "possible glitch" into the log message, to
make it more user-friendly.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>