xtensa: fix __sigsetjmp call12 case
xtensa: fix __sigsetjmp call12 case

Register window saving loop in __sigsetjmp incorrectly calculates offset
in the jmp_buf in case it was called with call12. The bug was introduced
in commit f4b1b7ade7971141 "xtensa: fix setjmp that didn't save all
registers correctly".

Signed-off-by: Max Filippov <8c5ea195856807f4f02a6e0749c87ea6b7375f38@gmail.com>

foss-for-synopsys-dwc-arc-processors/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,kraj/uclibc-ng,wbx-github/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,wbx-github/uclibc-ng,wbx-github/uclibc-ng,wbx-github/uclibc-ng,brgl/uclibc-ng,kraj/uclibc-ng,brgl/uclibc-ng,kraj/uclibc-ng,brgl/uclibc-ng,kraj/uclibc-ng,brgl/uclibc-ng