tools/include/uapi: Fix <asm/errno.h> for parisc and xtensa

tools/include/uapi/asm/errno.h currently attempts to include
non-existent arch-specific errno.h header for xtensa.
Remove this case so that <asm-generic/errno.h> is used instead,
and add the missing arch-specific header for parisc.

References: https://buildd.debian.org/status/fetch.php?pkg=linux&arch=ia64&ver=5.8.3-1%7Eexp1&stamp=1598340829&raw=1


Signed-off-by: Ben Hutchings <benh@debian.org>
Signed-off-by: Salvatore Bonaccorso <carnil@debian.org>
Cc: <stable@vger.kernel.org> # 5.10+
Signed-off-by: Helge Deller <deller@gmx.de>