Fix harmless warning in dwarf_cfi_to_module.cc.
Fix harmless warning in dwarf_cfi_to_module.cc.

This function already establishes that (signed) i must be positive by the time
it assigns it to (unsigned) reg. Because reg is unsigned, it is impossible for
it to be negative. Because i was already checked for positivity, this check
can be removed entirely. It was not a miswritten check that intended to check
i instead of reg, because i is already checked.

This addresses the following warning:

dwarf_cfi_to_module.cc:135:9: warning: comparison of 0 <= unsigned expression is always true [-Wtautological-compare]

Committed r859
Review URL: http://breakpad.appspot.com/310003

git-svn-id: 7939527bf0a06ad24ad020f729d5600cb42ed5d7@861 4c0a9323-5329-0410-9bdc-e9ce6186880e

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