Staging: comedi: s626.c: Remove unused functions

The functions s626_get_clk_mult, s626_get_clk_mult, s626_get_enc_mode,
s626_set_index_pol are not used anywhere in the kernel so they can be
removed. This also cleans the code. Grepped to find the occurences.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>