opentitan: Rename memmap enum constants

opentitan: Rename memmap enum constants

Some of the enum constant names conflict with the QOM type check
macros (IBEX_PLIC, IBEX_UART).  This needs to be addressed to
allow us to transform the QOM type check macros into functions
generated by OBJECT_DECLARE_TYPE().

Rename all the constants to IBEX_DEV_*, to avoid conflicts.

Reviewed-by: Alistair Francis <[email protected]>
Reviewed-by: Daniel P. Berrangé <[email protected]>
Signed-off-by: Eduardo Habkost <[email protected]>
Tested-By: Roman Bolshakov <[email protected]>
Message-Id: <20200825192110.3528606[email protected]>
Signed-off-by: Eduardo Habkost <[email protected]>