kernel/linux: add alternate download locations

Some longterm versions are not in the usual directory.
Account for these new locations.

Get rid of the mirror location, now that the main kernel site is
(almost) back to normal operations.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# Alpha specific configuration file

## select ARCH_SUPPORTS_32

## select ARCH_DEFAULT_32

## select ARCH_USE_MMU

## select ARCH_SUPPORTS_WITH_CPU

## select ARCH_SUPPORTS_WITH_TUNE

##

## help The Alpha architecture.