kernel.bbclass: Fix link for modules-${MACHINE}.tgz

The modules-${MACHINE}.tgz should link to ${MODULE_TARBALL_BASE_NAME}.
But now it links to an invalid file ${MODULE_TARBALL_BASE_NAME}.bin.
Remove the extra .bin suffix.

[YOCTO #4595]

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>