linux-user/hppa: Send proper si_code on SIGFPE exception

linux-user/hppa: Send proper si_code on SIGFPE exception

Improve the linux-user emulation to send the correct si_code depending
on overflow (TARGET_FPE_FLTOVF), underflow (TARGET_FPE_FLTUND), ...
Note that the hardware stores the relevant flags in FP exception
register #1, which is actually the lower 32-bits of the 64-bit fr[0]
register in qemu.

Signed-off-by: Helge Deller <deller@gmx.de>
(cherry picked from commit b4b49cf39dba5f993ad925f204cb820aacfc8e45)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>