ARM: dts: socfpga: Flag timer clock as pre-reloc

ARM: dts: socfpga: Flag timer clock as pre-reloc

Flag timer clock as DM pre-reloc, so that a timer driver can be used and
it can extract information about it's clock rate using the clock framework.
This patch also moves some of the pre-reloc flags into the core dtsi file,
this is because the timer is not board specific, but rather is used on all
boards.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <chin.liang.see@intel.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>