package/socat: Fix TABDLY, CSIZE and CRDLY shifts for PowerPC

As can be seen in linux/arch/powerpc/include/uapi/asm/termbits.h are
defined as (note that those are octal numbers):

\#define TABDLY	00006000
\#define CSIZE	00001400
\#define CRDLY	00030000

which gives shifts of 10, 8 and 12. Adjust socat.mk accordingly to
reflect that difference.

Signed-off-by: Mark Hinds <zoronic@gmail.com>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>