[riscv] Allow apply_relocs() to use non-inline relocation records

[riscv] Allow apply_relocs() to use non-inline relocation records

The address of the compressed relocation records is currently
calculated implicitly relative to the program counter.  This requires
the relocation records to be copied as part of relocation to a new
physical address, so that they can be reapplied (if needed) after
copying iPXE to the new physical address.

Since the relocation destination will never overlap the original iPXE
image, and since the relocation records will not be needed further
after completing relocation, we can avoid the need to copy the records
by passing in a pointer to the relocation records present in the
original iPXE image.

Pass the compressed relocation record address as an explicit parameter
to apply_relocs(), rather than being implicit in the program counter.

Signed-off-by: Michael Brown <mcb30@ipxe.org>