libutils: Implement speculation barrier for RISC-V

Implement load_no_speculate() with implementation consists of RISC-V
fence instructions which are used to preserve the memory order.

- Data barrie

libutils: Implement speculation barrier for RISC-V

Implement load_no_speculate() with implementation consists of RISC-V
fence instructions which are used to preserve the memory order.

- Data barrier: fence rw, rw
- Instruction barrier: fence.i; fence r, r

Signed-off-by: Alvin Chang <alvinga@andestech.com>
Reviewed-by: Yu Chien Peter Lin <peterlin@andestech.com>

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Prevent unused warnings in speculation_barrier.h

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Acked-by: Joakim Bech <joakim.b

Prevent unused warnings in speculation_barrier.h

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Acked-by: Joakim Bech <joakim.bech@linaro.org>

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libutils: import speculation_barrier.h

Import speculation_barrier.h from [1]. This file implements a set of
wrapper macros for the __builtin_load_no_speculate builtin function
detailed at [2]. This

libutils: import speculation_barrier.h

Import speculation_barrier.h from [1]. This file implements a set of
wrapper macros for the __builtin_load_no_speculate builtin function
detailed at [2]. This builtin function defines a speculation barrier,
which can be used to limit the conditions under which a value which has
been loaded can be used under specualtive execution.

The header file provided here allows a migration path to using the
builtin function for users who are unable to immediately upgrade to a
compiler which supports the builtin.

(Description taken from the README.md file of the speculation_barrier
project by Arm on GitHub [3])

Link: [1] https://raw.githubusercontent.com/ARM-software/speculation-barrier/80e65cd830b321ff676941c2fab773da450e6dae/speculation_barrier.h
Link: [2] https://www.arm.com/security-update
Link: [3] https://github.com/ARM-software/speculation-barrier
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Acked-by: Joakim Bech <joakim.bech@linaro.org>

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