Fix the UNW_TDEP_CURSOR_LEN for ppc32 to fix assert failure

When libunwind is built for a ppc32 target, for example the yocto distro
for qemuppc, and configured with options --enable-debug-frame and
--enable-debug, then the shortfall in the size of the 'opaque' member
of the unw_cursor_t type throws an assert in mi_init().

The calculations for the ppc32 target size of UNW_TDEP_CURSOR_LEN in
the comment block based on the register count plus overhead sum to 280
words. However, that value is not reflected in the ppc32 header, which
defines the size as 200.  Fixing the ppc32 header value to 280 makes the
unw_cursor_t type larger than struct cursor type and the assert tests
true at run-time in mi_init().

Signed-off-by Dave Lerner <dave.lerner@windriver.com>

include/libunwind-ppc32.h

@@ -62,7 +62,7 @@ extern "C" {
  * round that up to 280.
  */
 
-#define UNW_TDEP_CURSOR_LEN 200
+#define UNW_TDEP_CURSOR_LEN 280
 
 #if __WORDSIZE==32
 typedef uint32_t unw_word_t;