scripts: add possibility to not override default connection timeout

Allow '-1' to be specified as CONNECTION_TIMEOUT to disable the use
of the connection timeout for wget.

Signed-off-by: Cody P Schafer <dev@codyps.com>
Message-Id: <cb33f8c2cbaf802d4f04.1399687632@localhost>
Patchwork-Id: 347582

# Blackfin specific configuration file

## select ARCH_SUPPORTS_32

## select ARCH_DEFAULT_32

## select ARCH_DEFAULT_LE

## select ARCH_SUPPORTS_WITH_ARCH

## select ARCH_SUPPORTS_WITH_CPU

## select ARCH_SUPPORTS_WITH_TUNE

## select ARCH_SUPPORTS_WITH_FPU

##

## help The Blackfin architecture