riscv: remove special treatment for the link order of head.o

riscv: remove special treatment for the link order of head.o

arch/riscv/kernel/head.o does not need any special treatment - the only
requirement is the ".head.text" section must be placed before the
normal ".text" section.

The linker script does the right thing to do. The build system does
not need to manipulate the link order of head.o.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Link: https://lore.kernel.org/r/20221018141200.1040-1-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>