perf/x86/intel/uncore: Fix Add BW copypasta

gcc -Wextra points out a duplicate initialization of one array
member:

arch/x86/events/intel/uncore_snb.c:478:37: warning: initialized field overwritten [-Woverride-init]
  478 |  [SNB_PCI_UNCORE_IMC_DATA_READS]  = { SNB_UNCORE_PCI_IMC_DATA_WRITES_BASE,

The only sensible explanation is that a duplicate 'READS' was used
instead of the correct 'WRITES', so change it back.

Fixes: 24633d90 ("perf/x86/intel/uncore: Add BW counters for GT, IA and IO breakdown")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201026215203.3893972-1-arnd@kernel.org