target/hppa: Fix DCOR reconstruction of carry bits

target/hppa: Fix DCOR reconstruction of carry bits

The carry bits for each nibble N are located in bit (N+1)*4,
so the shift by 3 was off by one.  Furthermore, the carry bit
for the most significant carry bit is indeed located in bit 64,
which is located in a different storage word.

Use a double-word shift-right to reassemble into a single word
and place them all at bit 0 of their respective nibbles.

Tested-by: Helge Deller <deller@gmx.de>
Reviewed-by: Helge Deller <deller@gmx.de>
Fixes: b2167459ae4 ("target-hppa: Implement basic arithmetic")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>