dt-bindings: timer: Move snps,dw-apb-timer DT schema from rtc

This binding file doesn't belong to the rtc seeing it's a pure timer
with no rtc facilities like days/months/years counting and alarms.
So move the YAML-file to the Documentation/devicetree/bindings/timer/
directory.

Signed-off-by: Serge Semin <[e-mail]>
Acked-by: Alexandre Belloni <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Cc: Alexey Malahov <[e-mail]>
Cc: Thomas Bogendoerfer <[e-mail]>
Cc: Paul Burton <[e-mail]>
Cc: Ralf Baechle <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: [e-mail]
Signed-off-by: Daniel Lezcano <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/rtc/snps,dw-apb-timer.yaml Documentation/devicetree/bindings/timer/snps,dw-apb-timer.yaml

···
 # SPDX-License-Identifier: GPL-2.0-only
 %YAML 1.2
 ---
-$id: http://devicetree.org/schemas/rtc/snps,dw-apb-timer.yaml#
+$id: http://devicetree.org/schemas/timer/snps,dw-apb-timer.yaml#
 $schema: http://devicetree.org/meta-schemas/core.yaml#
 
 title: Synopsys DesignWare APB Timer