PowerPC: Fix termios definitions

This patch fixes the incorrect guard by __USE_MISC of struct winsize and
struct termio in powerpc termios header.  Current states leads to build
failures if the program defines _XOPEN_SOURCE, but not _DEFAULT_SOURCE
or either _BSD_SOURCE or _SVID_SOURCE.  Without any definition,
__USE_MISC will not be defined and neither the struct definitions.

This patch copies the default Linux ioctl-types.h by adjusting only the
character control field (c_cc) size in struct termio.