linux-firmware: amd-ucode: Add note on fam19h warnings

When running 5.19+ kernels on Genoa or Bergamo systems, some microcode
patches are known to trigger warnings in the PMI handler. Add a note
to list the required minimum patch levels for addressing this problem.

Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Josh Boyer <jwboyer@kernel.org>