hw/misc: Implement mailbox properties for customer OTP and device specific private keys
Four mailbox properties are implemented as follows:
1. Customer OTP: GET_CUSTOMER_OTP and SET_CUSTOMER_OTP
2. Device-specific private key: GET_PRIVATE_KEY and
SET_PRIVATE_KEY.
The customer OTP is located in the rows 36-43. The device-specific private key
is located in the rows 56-63.
The customer OTP can be locked with the magic numbers 0xffffffff 0xaffe0000
when running the SET_CUSTOMER_OTP mailbox command. Bit 6 of row 32 indicates
this lock, which is undocumented. The lock also applies to the device-specific
private key.
Signed-off-by: Rayhan Faizel <rayhan.faizel@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>