riscv: Remove duplicate CONFIG_PAGE_OFFSET definition

This definition is already provided by include/generated/autoconf.h,
so it does not need to be provided on the command line.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Jesse Taube <mr.bossman075@gmail.com>
Link: https://lore.kernel.org/r/20241026171441.3047904-2-samuel.holland@sifive.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>