Provide the ability to constrain the total number of enabled devices in
the system. Once max_devs devices have been configured, subsequently
probed devices are ignored.

The max_devs parameter may be zero, in which case all CCPs are disabled.
PSPs are always enabled and active.

Disabling the CCPs also disables DMA and RNG registration.
Signed-off-by: Gary R Hook <gary.hook@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>