Staging: ks7010: Remove extern keyword from function declaration

Remove extern specifier from function declaration as they have
it by default. Also move extern declaration from .c files to
their respective header file 'ks_hostif.h'. Coccinelle was used
to remove extern and other changes were done by hand.
Script:
@@
identifier func;
type T;
@@
- extern
T func(...);

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