perf_counter tools: Fix uninitialized variable in perf-report.c

# make prefix=/usr/local V=1
gcc -o builtin-report.o -c -O2 -ggdb3 -Wall -Werror -Wstrict-prototypes -Wmissing-declarations -Wmissing-prototypes -std=gnu99 -Wdeclaration-after-statement   -DSHA1_HEADER='<openssl/sha.h>'  builtin-report.c
cc1: warnings being treated as errors
builtin-report.c: In function ‘__cmd_report’:
builtin-report.c:626: error: ‘cwdlen’ may be used uninitialized in this function

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <new-submission>