linux-at91: bump version to linux4sam_6.1
linux-at91: bump version to linux4sam_6.1

Signed-off-by: Razvan Stefanescu <f4ee3fcb6e54dcf71fbaefdd500eea5cee1f4f99@microchip.com>

linux4sam/meta-atmel,linux4sam/meta-atmel,linux4sam/meta-atmel,linux4sam/meta-atmel,linux4sam/meta-atmel