boot_nv_security_counter_init() not called through boot_go()

[Olstyle]

If MCUBOOT_HW_ROLLBACK_PROT is defined, one is expected to implement the interface from security_cnt.h. This interface also defines the function boot_nv_security_counter_init().
But actually that function is never called from the boot code. I can of course call it myself before boot_go() and have a functioning system, but if it is supposed to be an expected interface I also expect it to be called.

This is a copy of #1872 since it was closed by (silly) automation and I can not reopen it.