samples: userspace: cortex_r8_virtual: Set CONFIG_DYNAMIC_OBJECTS=y

Enable kernel dynamic object allocation.
Otherwise the following error is printed:

    E: 0xa138 is not a valid sample driver
    E: address is not a known kernel object
    E: syscall z_vrfy_sample_driver_state_set failed check: access denied
    E: couldn't start driver interrupts

Signed-off-by: Marek Slowinski <mslowinski@antmicro.com>
Signed-off-by: Mateusz Hołenko <mholenko@antmicro.com>