arm64/ptrace: Avoid uninitialised struct padding in fpr_set()

This patch adds an explicit __reserved[] field to user_fpsimd_state
to replace what was previously unnamed padding.

This ensures that data in this region are propagated across
assignment rather than being left possibly uninitialised at the
destination.

Cc: <[e-mail]> # 3.7.x-
Fixes: 60ffc30d5652 ("arm64: Exception handling")
Signed-off-by: Dave Martin <[e-mail]>
Acked-by: Will Deacon <[e-mail]>
Signed-off-by: Catalin Marinas <[e-mail]>

arch/arm64/include/uapi/asm/ptrace.h

···
 	__uint128_t	vregs[32];
 	__u32		fpsr;
 	__u32		fpcr;
+	__u32		__reserved[2];
 };
 
 struct user_hwdebug_state {