packages: apply custom patches using *.patch instead of <pkg>-*.patch

Several packages have some logic to apply custom patches that existed
before the BR2_GLOBAL_PATCH_DIR mechanism: at91bootstrap,
at91bootstrap3, barebox, uboot and linux. Currently, the logic of
those packages to apply custom patches is to match
<package-name>-*.patch, which is not consistent with what we've done
for patches stored in the package directory, and for patches stored in
BR2_GLOBAL_PATCH_DIR: in such cases, we simply apply *.patch.

Therefore, for consistency reasons, this commit changes these packages
to also apply *.patch.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>