Ignore amd & intel ucode initrd's, making this work on systems with ucodes installed

[mini-bomba]

I've made this script ignore any intel or amd microcode images, making it work on distros with such packages installed (such as Arch Linux with amd-ucode installed). This fixes the major issue mentioned in #8 (the script failing when microcode is installed), but does not actually implement multiple initrd support. It simply removes any initrd's named intel-ucode.img or amd-ucode.img from the argument list.

As this comment on issue #8 states, microcodes persist kexec's and cannot be loaded twice, so this should be fine.

Only affects GRUB 2, tested on two Arch Linux installations with GRUB 2, one with only amd-ucode and one with both intel-ucode and amd-ucode. Does not affect initrd's on GRUB 1 (since i do not have a system with GRUB 1)