arc: clone: Recover PID correctly
arc: clone: Recover PID correctly

Caught by tst-getpid1 test from uClibc's test-suite.

It looks like original implementation was not correct.
The code in question is supposed to recover PID of the new
thread. And by no means that could happen with clone() syscall
while getpid() does exactly this.

Signed-off-by: Alexey Brodkin <1fa739873496c8c0c1b521f2061ee5fa4a0306e8@synopsys.com>
Acked-by: Vineet Gupta <af669d95a4c0de051445d4cafdbb2c5c4a2838be@synopsys.com>
Reported-by: Eugeniy Paltsev <125c665cd16bc5380c00ca356609c49ed90d4ffa@synopsys.com>

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