RHEL9/PPC64LE: cannot install RHEL9, the kernel panics after Grub initially prints "error: ../../grub-core/kern/mm.c:552:out of memory."

Issue

• Trying to install RHEL9 on the PPC64LE Power 10 system, the kernel panics

  [    0.206828] List of all partitions:
  [    0.206831] No filesystem could mount root, tried:
  [    0.206832]
  [    0.206835] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
  [    0.206842] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.14.0-503.11.1.el9_5.ppc64le #1
  [    0.206854] Call Trace:
  [    0.206858] [c0000000038d7b20] [c0000000008efe70] dump_stack_lvl+0x74/0xa8
  [    0.206871] [c0000000038d7b60] [c000000000155998] panic+0x17c/0x454
  [    0.206885] [c0000000038d7c00] [c000000002005d50] mount_root_generic+0x260/0x294
  [    0.206894] [c0000000038d7cd0] [c000000002006258] prepare_namespace+0x2b0/0x320
  [    0.206901] [c0000000038d7d50] [c000000002005608] kernel_init_freeable+0x264/0x2a4
  [    0.206908] [c0000000038d7db0] [c000000000012760] kernel_init+0x30/0x1a0
  [    0.206914] [c0000000038d7e10] [c00000000000cd64] ret_from_kernel_thread+0x5c/0x64
  [    0.212792] Rebooting in 10 seconds..
  

• Initially Grub reported the following error message

  error: ../../grub-core/kern/mm.c:552:out of memory.
  
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