openrisc: Define openrisc relocation types

This defines the current OpenRISC relocation types using the current
R_OR1K_* naming conventions.

The old R_OR32_* definitions are left for backwards compatibility.
Note, the R_OR32_VTENTRY and R_OR32_VTINHERIT macros were defined with
the wrong values the have always been 7 and 8 respectively, not 8 and 7.
They are not used for module loading and I have updated them to use the
correct values.

Signed-off-by: Stafford Horne <shorne@gmail.com>