riscv: Fix __always_inline causes duplicate inline

riscv: Fix __always_inline causes duplicate inline

In file included from /usr/include/features.h:503,
from /usr/include/bits/libc-header-start.h:33,
from /usr/include/stdint.h:26,
from /usr/lib64/gcc/riscv64-suse-linux/13/include/stdint.h:9,
from ../../../tests/unit/arch-mo.c:5,
from ../../../tests/unit/arch-mo-cxx.cpp:5:
../../../include/rseq/rseq-riscv-bits.h:9:15: error: duplicate 'inline'
9 | static inline __always_inline
| ^~~~~~~~~~~~~~~

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Iabf16e221e6a84ac31163d58c7e6edf2e87c5d18