MIPS: Add M6250 PRID & cpu_type_enum values

MIPS: Add M6250 PRID & cpu_type_enum values

Define the processor ID for the M6250 CPU and add a value to the enum
cpu_type_enum for the core.

[[email protected]: Fix merge conflict.]

Signed-off-by: Paul Burton <[email protected]>
Cc: Joshua Kinard <[email protected]>
Cc: Leonid Yegoshin <[email protected]>
Cc: James Hogan <[email protected]>
Cc: [email protected]
Cc: [email protected]
Patchwork: https://patchwork.linux-mips.org/patch/12373/
Signed-off-by: Ralf Baechle <[email protected]>