Code review in dsa.c

Hi, hackers

Found  some functions in dsa.c are not used anymore.

dsa_create
dsa_attach
dsa_get_handle
dsa_trim
dsa_dump

We once used dsa_create to create DSA and  it ’s all replaced by dsa_create_in_place since commit 31ae1638ce.
dsa_attach and dsa_get_handle cooperate with dsa_create.
dsa_trim and dsa_dump are introduced by DSA original commit 13df76a537 , but not used since then.

So, they are all dead codes, provide a patch to remove them.

Zhang Mingli