target-sparc: fix fcmp{s,d,q} instructions wrt exception

fcmp{s,d,q} instructions are supposed to ignore quiet NaN (contrary to
the fcmpe{s,d,q} instructions), but the current code is wrongly setting
the NV exception in that case. Moreover the current code is duplicated:
first the arguments are checked for NaN to generate an exception, and
later in case the comparison is unordered (which can only happens if one
of the argument is a NaN), the same check is done to generate an
exception.

Fix that by calling clear_float_exceptions() followed by
check_ieee_exceptions() as for the other floating point instructions.
Use the _compare_quiet functions for fcmp{s,d,q} and the _compare ones
for fcmpe{s,d,q}. Simplify the flag setting by not clearing a flag that
is set the line just below.

This fix allows the math glibc testsuite to pass.

Cc: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
