build(deps): Use safe-mmio fork that forces little endian MMIO

Until we figure out a way to handle this nicely in arm-gic and related
crates.

Signed-off-by: Jens Reidel <[email protected]>

Author: Gelbpunkt

Cargo.lock

@@ -216,3 +216,4 @@ exclude = [
 x86_64 = { git = "https://github.com/rust-osdev/x86_64.git" }
 # FIXME: remove once merged: https://github.com/rcore-os/trapframe-rs/pull/16
 trapframe = { git = "https://github.com/hermit-os/trapframe-rs", branch = "global_asm" }
+safe-mmio = { git = "https://github.com/hermit-os/safe-mmio", branch = "be" }