dt-bindings: clock: fix some conversion style issues for rockchip,rk3399-cru.yaml

With the conversion of rockchip,rk3399-cru.txt a table with external clocks
was copied. Make it a bit cleaner by aligning the columns. Also fix
a description. Phrases start with a capital.

Signed-off-by: Johan Jonker <[e-mail]>
Acked-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Heiko Stuebner <[e-mail]>

Documentation/devicetree/bindings/clock/rockchip,rk3399-cru.yaml

···
   There are several clocks that are generated outside the SoC. It is expected
   that they are defined using standard clock bindings with following
   clock-output-names:
-    - "xin24m" - crystal input - required,
-    - "xin32k" - rtc clock - optional,
-    - "clkin_gmac" - external GMAC clock - optional,
-    - "clkin_i2s" - external I2S clock - optional,
-    - "pclkin_cif" - external ISP clock - optional,
+    - "xin24m"           - crystal input                          - required,
+    - "xin32k"           - rtc clock                              - optional,
+    - "clkin_gmac"       - external GMAC clock                    - optional,
+    - "clkin_i2s"        - external I2S clock                     - optional,
+    - "pclkin_cif"       - external ISP clock                     - optional,
     - "clk_usbphy0_480m" - output clock of the pll in the usbphy0
     - "clk_usbphy1_480m" - output clock of the pll in the usbphy1
 
···
 
   rockchip,grf:
     $ref: /schemas/types.yaml#/definitions/phandle
-    description: >
-      phandle to the syscon managing the "general register files". It is used
+    description:
+      Phandle to the syscon managing the "general register files". It is used
       for GRF muxes, if missing any muxes present in the GRF will not be
       available.