arm64: uprobe: Return EOPNOTSUPP for AARCH32 instruction probing

As stated in linux/errno.h, ENOTSUPP should never be seen by user programs.
When we set up uprobe with 32-bit perf and arm64 kernel, we would see the
following vague error without useful hint.

The sys_perf_event_open() syscall returned with 524 (INTERNAL ERROR:
strerror_r(524, [buf], 128)=22)

Use EOPNOTSUPP instead to indicate such cases.
Signed-off-by: NHe Zhe <zhe.he@windriver.com>
Link: https://lore.kernel.org/r/20210223082535.48730-1-zhe.he@windriver.com
Cc: <stable@vger.kernel.org>
Signed-off-by: NWill Deacon <will@kernel.org>

arch/arm64/kernel/probes/uprobes.c

@@ -38,7 +38,7 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
 
 	/* TODO: Currently we do not support AARCH32 instruction probing */
 	if (mm->context.flags & MMCF_AARCH32)
-		return -ENOTSUPP;
+		return -EOPNOTSUPP;
 	else if (!IS_ALIGNED(addr, AARCH64_INSN_SIZE))
 		return -EINVAL;