main/openssh: remove zero-call-used-regs_all.patch

I assume this patch was needed because Clang version detection was broken upstream because our Clang version string additionally contains the word "Alpine". This has been fixed upstream.

See: https://github.com/openssh/openssh-portable/commit/2a19e02f36b16f0f6cc915f7d1e60ead5e36303b

Nowadays, the compiler error mentioned in the patch description doesn't appear anymore (even on ppc64le where I tested this extensively). The configure script correctly detects that this option is not supported on ppc64le.