Revert "parisc: Add assembly implementations for memset, strlen, strcpy, strncpy and strcat"

This reverts commit 83af58f8068ea3f7b3c537c37a30887bfa585069.

It turns out that at least the assembly implementation for strncpy() was
buggy. Revert the whole commit and return back to the default coding.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # v5.4+
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>