arch/arm/mach-omap2/omap5/fdt.c: ft_fixup_clocks: use clock-output-names property...

arch/arm/mach-omap2/omap5/fdt.c: ft_fixup_clocks: use clock-output-names property as fallback (kernel 5.19+)

Clock names has been updated in kernel 5.19+ with the removal of
non-standard node names [1]. Due to this change, ft_opp_clock_fixups()
doesn't work anymore since ft_fixup_clocks() is looking to the clock
name and ft_opp_clock_fixups() error out with the following message:

  ft_fixup_clocks failed for DSP voltage domain: <valid offset/length>

We can't use the new clock name since several clock are using the same
generic name "clock". ft_opp_clock_fixups() is looking at the clocks
node in cm_core_aon@0:

/sys/firmware/devicetree/base/ocp/interconnect@4a000000/segment@0/target-module@5000/cm_core_aon@0/clocks
  ...
  clock@120
  clock@160
  clock@1a0
  clock@1e0
  clock@210
  clock@234
  clock@284
  clock@2a8
  clock@2d8

When fdt_subnode_offset() fail, we can look at clock-output-names
property as fallback since it contain the previous clock name.

libfdt doesn't provide any support to replace fdt_subnode_offset() by
a new function looking for clock-output-names property instead of the
node name. So we have to implement it in arch/arm/mach-omap2/omap5/fdt.c
for now.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e4920169e7a2a839836d3a0d8cda1bae8caa3056

Cc: Suman Anna <s-anna@ti.com>
Cc: Tom Rini <trini@konsulko.com>
Cc: Andrew Davis <afd@ti.com>
Signed-off-by: Romain Naour <romain.naour@skf.com>