Revert "riscv: sifive: fu540: Add gpio-restart support"

As part of merging the next branch in to master, the sifive_fu540 will
fail to link:
riscv64-linux-ld.bfd: lib/built-in.o: in function `panic_finish':
lib/panic.c:28: undefined reference to `do_reset'
make[2]: *** [spl/u-boot-spl] Error 1
make[1]: *** [spl/u-boot-spl] Error 2
make: *** [sub-make] Error 2

And while the "fix the build" option of enabling CONFIG_SPL_SYSRESET may
solve the issue, it is unclear that it is the correct path exactly.  For
the moment, I am reverting this commit and take a "revert the revert"
and proper fix as soon as it's available.

This reverts commit cdae4464.

Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Anup Patel <anup.patel@wdc.com>
Cc: Atish Patra <atish.patra@wdc.com>
Cc: Bin Meng <bin.meng@windriver.com>
Signed-off-by: Tom Rini <trini@konsulko.com>