Fix BZ #29463 in the ibm128 implementation of y1l too

Avoid moving code across SET_RESTORE_ROUNDL in order to fix
[BZ #29463].

Tested-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
(cherry picked from commit b6e37b78)