Fix issue #1853.

Commit 7c489469 ("adjust tracepoint field type
based on size") tried to fix the tracepoint format
descrepancy between declared type and actual size is 8.
The type has to be promoted to match the size.

The commit introduced a bug if the field is an array.
For exmaple, block:block_rq_complete tracepoint has
field rwbs:
  field:char rwbs[8];	offset:32;	size:8;	signed:1;

The current implementation will incorrectly translate it
into
  s64 rwbs[8];
since it considers the type is "char".

This patch fixed this issue by checking the field name
and if it is an array, rewriting will be skipped.
Signed-off-by: Yonghong Song <yhs@fb.com>