openrisc: Fix issue with argument clobbering for clone/fork

[ Upstream commit 6bd140e14d9aaa734ec37985b8b20a96c0ece948 ]

Working on the OpenRISC glibc port I found that sometimes clone was
working strange.  That the tls data argument sent in r7 was always
wrong.  Further investigation revealed that the arguments were getting
clobbered in the entry code.  This patch removes the code that writes to
the argument registers.  This was likely due to some old code hanging
around.

This patch fixes this up for clone and fork.  This fork clobber is
harmless but also useless so remove.

Signed-off-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>