templates/GRML/grml-cheatcodes.txt: document kernel parameter dis_uco…

…de_ldr

The dis_ucode_ldr kernel parameter disables the microcode loader, see
https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html
and
https://wiki.debian.org/Microcode#Working_around_boot_problems_caused_by_microcode_updates

We don't ship the amd64-microcode + intel-microcode Debian packages on
Grml, so we don't need to enable this option by default, but let's
document it just in case.

Related resources:

* https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1831789
* https://lists.ubuntu.com/archives/ubuntu-devel/2019-June/040725.html

templates/GRML/grml-cheatcodes.txt

@@ -230,6 +230,7 @@ grml libata.force=[ID:]VAL            Force configurations for libata.
                                       to force pio4 mode on device "ata1:00:"
 grml libata.dma=0                     Disable DMA on PATA and SATA devices
 grml libata.ignore_hpa=1              Disable host protected area (which should enable the whole disk)
+grml dis_ucode_ldr                    Disable the microcode loader
 grml vga=normal                       No-framebuffer mode (does not influence X)
 grml vga=ask                          Display menu for framebuffer mode
 grml radeon.modeset=0  nomodeset      Disable Kernel Mode Setting (KMS) for Radeon driver.