arm: dts: k3-j721s2-r5: Change GTC clock parent

arm: dts: k3-j721s2-r5: Change GTC clock parent

MAIN_PLL0 has a flag set in DM (Device Manager) that removes its
capability to re-initialise clock frequencies. A72 CPU clock (GTC) and
RGMII has MAIN_PLL3 as their parent which does not have this flag. While
RGMII needs re-initialization to default frequency to be able to get
250MHz with its divider, GTC can not get its required 200MHz with its
dividers. Thus move GTC clock parent on J721S2 from MAIN_PLL3_HSDIV1 to
MAIN_PLL0_HSDIV6. This was already done on CPTS node in kernel which was
similarly affected (linked).

Link: https://lore.kernel.org/all/20230605110443.84568-1-n-francis@ti.com/
Signed-off-by: Neha Malcom Francis <n-francis@ti.com>