Use current SP instead of global data ptr for the U-Boot API signature search hint.
Use current SP instead of global data ptr for the U-Boot API signature search hint.

Global data (pointed by R2 on PowerPC) in principle is not guaranteed to be in
proximity of U-Boot heap (where the API signature is placed) accross different
architectures and platforms. Instead, use U-Boot stack pointer as a hint for
the search instead of the global data; this method tends to be more uniform
accross different platforms.

Obtained from:	Semihalf

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