arm64: dts: ti: k3-am64-main: Switch ICSSG clock to core clock

arm64: dts: ti: k3-am64-main: Switch ICSSG clock to core clock

ICSSG has 7 available clocks per instance. Add all the cloks to ICSSG
nodes. ICSSG currently uses ICSSG_ICLK (clk id 20) which operates at
250MHz. Switch ICSSG clock to ICSSG_CORE clock (clk id 0) which operates at
333MHz.

ICSSG_CORE clock will help get the most out of ICSSG as more cycles are
needed to fully support all ICSSG features.

This commit also changes assigned-clock-parents of coreclk-mux to
ICSSG_CORE clock from ICSSG_ICLK.

Performance update in dual mac mode
  With ICSSG_CORE Clk @ 333MHz
    Tx throughput - 934 Mbps
    Rx throughput - 914 Mbps,

  With ICSSG_ICLK clk @ 250MHz,
    Tx throughput - 920 Mbps
    Rx throughput - 706 Mbps

Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Tested-by: Wadim Egorov <w.egorov@phytec.de>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Link: https://lore.kernel.org/r/20241113110955.3876045-3-danishanwar@ti.com
Signed-off-by: Nishanth Menon <nm@ti.com>