integer-gmp: Fix style
integer-gmp: Fix style

Just fix a few inconsistencies that I encountered.

[skip ci]

Reviewers: austin, hvr, goldfire

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D4024

sdiehl/ghc,sdiehl/ghc,ezyang/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,ezyang/ghc,sdiehl/ghc,shlevy/ghc