fix: drop cfg(target_arch) from create_guest_memfd

The KVM docs do not list this ioctls as restricted to any specific
architecture. It is instead discoverable via capabilities, and can
theoretically work on any architecture (provided the architecture has a
VM type that support guest private memory).

Signed-off-by: Patrick Roy <roypat@amazon.co.uk>

src/ioctls/vm.rs

@@ -1474,7 +1474,6 @@ impl VmFd {
     ///
     /// let guest_memfd = vm.create_guest_memfd(gmem).unwrap();
     /// ```
-    #[cfg(any(target_arch = "x86_64", target_arch = "aarch64"))]
     pub fn create_guest_memfd(&self, gmem: kvm_create_guest_memfd) -> Result<RawFd> {
         // SAFETY: Safe because we know that our file is a VM fd, we know the kernel will only
         // read the correct amount of memory from our pointer, and we verify the return result.