PowerPC, correct the gdb ioctl values for TCGETS, TCSETS, TCSETSW and TCSETSF.

PowerPC, correct the gdb ioctl values for TCGETS, TCSETS, TCSETSW and TCSETSF.

Some of the ioctl numbers are based on the size of kernel termios structure.
Currently the PowerPC GDB definitions are "hard coded" into the ioctl
number.

The current PowerPC values for TCGETS, TCSETS, TCSETSW and TCSETSF are
defined in gdb/ppc-linux-tdep.c as:

  record_tdep->ioctl_TCGETS = 0x403c7413;
  record_tdep->ioctl_TCSETS = 0x803c7414;
  record_tdep->ioctl_TCSETSW = 0x803c7415;
  record_tdep->ioctl_TCSETSF = 0x803c7416;

Where the termios structure size is in hex digits [5:4] as 0x3c.

The definition for the PowerPC termios structure is given in:
  arch/powerpc/include/uapi/asm/termbits.h

The size of the termios data structure in this file is 0x2c not 0x3c.

This patch changes the hex digits for the size of the PowerPC termios size
in the ioctl values for TCGETS, TCSETS, TCSETSW and TCSETSF to 0x2c.
This patch also changes the hard coding to generate the number based on a
it easier to update the ioctl numbers.