UB caused by Status enum

[GabrielMajeri]

The status codes returned on error are currently defined as an enum, but as @HadrienG2 pointed out, UEFI functions are allowed to return implementation-specific error codes, or error codes not listed in a function's specification. This could trigger undefined behavior.

[HadrienG2]

I can look into this one once I'm done fixing some avenues for memory unsafety in the safe GOP interface.