This patch amends commit dfd3426aa5 which added support for running
with some signals disabled to AVR architecture. AVR DA/DB architecture
was not covered by the commit and failed to build
with CONFIG_ENABLE_ALL_SIGNALS unset (which includes building
with CONFIG_ENABLE_PARTIAL_SIGNALS, the default value.)
Change is replicated from the commit and tested by a custom stress
application which spawns some always-busy threads and uses preemptive
multitasking to switch between them. Additionally, ability to sleep
in the application was tested by a simple LED blinking application.
Signed-off-by: Kerogit <kr.git@kerogit.eu>