elf: Improve symbol lookup (optimize, fix for bsd-user)

Coverity complained about local variable key which was only partially
initiated. Only key.st_value was set. As this was also the only part
of key which was used in function symfind, the code could be optimized
by directly passing a pointer to orig_addr.

In bsd-user/elfload.c, fix ec822001
was missing. This was a simple replacement of > by >= in symfind, so
I fixed it here without creating an additional patch.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Andrzej Zaborowski <andrew.zaborowski@intel.com>