efi: Add linux memory reserve table defniitions

There is some hardware which can't be completely reset to release the
memory it is using(so far only the GICv3 on arm has fit this
bill). Since that meory needs to be reserved by the OS for that
hardware's later use of it, create defines for code that will parse that
memory table. Otherise the system may allocate the memory for block I/O,
network packets, etc which will lead to memory corruption.

When booting via Linux's kexec protocol, it will add this table to the
EFI systbl's cfgtbl array. While the mechanism to pass 'configuration'
is standardized, these specific tables are not documented except in the
Linux source. Include comments gleened from its study.

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