Introduce `CONFIG_RISCV_GP_PURPOSE` choice to make sure that only
one of `CONFIG_RISCV_GP` or `CONFIG_RISCV_CURRENT_VIA_GP` can be
enabled, instead of relying of dependencies.
To do that, introduce a new
`CONFIG_RISCV_SOC_HAS_GP_RELATIVE_ADDRESSING` that can be selected
by SoC when it implemented global pointer (GP) initialization for
relative addressing in its linker.
`CONFIG_RISCV_GP` will be the default choice when
`CONFIG_RISCV_SOC_HAS_GP_RELATIVE_ADDRESSING=y`
Signed-off-by: Yong Cong Sin <ycsin@meta.com>
Signed-off-by: Yong Cong Sin <yongcong.sin@gmail.com>
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