MLK-22484: arm64: dts: Fix mem clock for asrc

MLK-22484: arm64: dts: Fix mem clock for asrc

The mem clock is used to access the register, if there is no
mem clock defined, we should use the ipg clock instead,
otherwise there will be kernel dump after system reboot.

[    3.010962] Kernel panic - not syncing: Asynchronous SError Interrupt
[    3.010964] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.19.35-05057-g2134d856e6b2 #2889
[    3.010966] Hardware name: Freescale i.MX8QXP MEK (DT)
[    3.010968] Call trace:
[    3.010969]  dump_backtrace+0x0/0x178
[    3.010971]  show_stack+0x14/0x20
[    3.010972]  dump_stack+0x8c/0xac
[    3.010974]  panic+0x120/0x28c
[    3.010975]  __stack_chk_fail+0x0/0x18
[    3.010977]  arm64_serror_panic+0x74/0x80
[    3.010979]  do_serror+0x68/0x130
[    3.010980]  el1_error+0x7c/0xdc
[    3.010982]  _raw_spin_unlock_irqrestore+0xc/0x48
[    3.010984]  clk_core_disable_lock+0x28/0x38
[    3.010985]  clk_disable+0x1c/0x30
[    3.010987]  regmap_mmio_write+0x54/0x68
[    3.010989]  _regmap_bus_reg_write+0x14/0x20
[    3.010990]  _regmap_write+0x60/0xa8
[    3.010992]  regmap_write+0x48/0x70
[    3.010994]  fsl_asrc_probe+0x258/0x660
[    3.010995]  platform_drv_probe+0x50/0xb0

Why this issue only happen at kernel reboot, it is because the ipg
clock is enabled in default after system reset, after used once, the
ipg clock is disabled, then reboot system, the issue happen.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>