pci: Fix clippy warning while comparing raw pointers

Use the builtin function instead of using `==` operator.

Warning from the beta compiler:

error: use `std::ptr::eq` when comparing raw pointers
--> pci/src/vfio.rs:1616:24

if host_addr == libc::MAP_FAILED {
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    help: try: `std::ptr::eq(host_addr, libc::MAP_FAILED)`

 = help: for further information visit
 = https://rust-lang.github.io/rust-clippy/master/index.html#ptr_eq
 = note: `-D clippy::ptr-eq` implied by `-D warnings`
 = help: to override `-D warnings` add `#[allow(clippy::ptr_eq)]`

Signed-off-by: Jinank Jain <jinankjain@microsoft.com>

hypervisor/src/mshv/mod.rs

@@ -1813,7 +1813,7 @@ impl vm::Vm for MshvVm {
                     MSHV_VP_MMAP_OFFSET_GHCB as i64 * libc::sysconf(libc::_SC_PAGE_SIZE),
                 )
             };
-            if addr == libc::MAP_FAILED {
+            if std::ptr::eq(addr, libc::MAP_FAILED) {
                 // No point of continuing, without this mmap VMGEXIT will fail anyway
                 // Return error
                 return Err(vm::HypervisorVmError::MmapToRoot);

pci/src/vfio.rs

@@ -1613,7 +1613,7 @@ impl VfioPciDevice {
                         )
                     };
 
-                    if host_addr == libc::MAP_FAILED {
+                    if std::ptr::eq(host_addr, libc::MAP_FAILED) {
                         error!(
                             "Could not mmap sparse area (offset = 0x{:x}, size = 0x{:x}): {}",
                             area.offset,

pci/src/vfio_user.rs

@@ -169,7 +169,7 @@ impl VfioUserPciDevice {
                         )
                     };
 
-                    if host_addr == libc::MAP_FAILED {
+                    if std::ptr::eq(host_addr, libc::MAP_FAILED) {
                         error!(
                             "Could not mmap regions, error:{}",
                             std::io::Error::last_os_error()