config.guess: automatic fixups after previous automated patch

This patch was generated using the following command:

  sed -i config.guess \
      -e '/="[^"]\+"\(-\|$\)/s/="\([^"([:space:])]\+\)"/=\1/' \
      -e '/="[^"]\+"[[:alnum:]]/s/="\$\([^([:space:])]\+\)"/=${\1}/' \
      -e \
'/\$(echo[^|]\+|/s/\([^[:space:]]\)[[:space:]]*|[[:space:]]*sed/\1 | sed/g'

* config.guess: Remove unneeded quotes in other variable assignments,
standardize spacing for "echo ... | sed" substitutions.