ANDROID: random: add back removed callback functions

Commit 6da877d2 ("random: replace custom notifier chain with
standard one") in 5.15.44 removed the add_random_ready_callback() and
del_random_ready_callback() functions, which are part of the current
Android ABI in this branch.  To handle this properly, add them back in
order for out-of-tree code to continue working.

Bug: 161946584
Fixes: 6da877d2 ("random: replace custom notifier chain with standard one")
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I422f3af1a28c5cf2e7f7806d6fb37d66901e3a33