ENOTSUPP (double PP) is internal linux kernel code 524 available only in
kernel include file linux/errno.h and not exported to userspace.

EOPNOTSUPP (OP; double PP) is standard code 95 for reporting 'operation not
supported' available via kernel include file uapi/asm-generic/errno.h.

ENOTSUP (single P) is alias for EOPNOTSUPP defined only in userspace
include file bits/errno.h and not available in kernel.

Because Linux kernel does not support ENOTSUP (single P) and because
userspace does not support ENOTSUPP (double PP), report error code for
'operation not supported' via EOPNOTSUPP macro.

This patch fixes problem that mwifiex kernel driver sends to userspace
unsupported error codes like: "failed: -524 (No error information)".
After applying this patch userspace see: "failed: -95 (Not supported)".
Signed-off-by: Pali Rohár <pali@kernel.org>
Acked-by: Ganapathi Bhat <ganapathi.bhat@nxp.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200703112151.18917-1-pali@kernel.org