buildroot

wf111: properly define and use the WF111_VERSION variable

Instead of hardcoding again the version of the package when defining
WF111_SOURCE, this commit changes the WF111_VERSION so that it
contains the entire version number, and then modifies the WF111_SOURCE
definitions to use WF111_VERSION.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>