build(deps): bump x86_64 from 0.12.2 to 0.12.3

Bumps [x86_64](https://github.com/rust-osdev/x86_64) from 0.12.2 to 0.12.3.
- [Release notes](https://github.com/rust-osdev/x86_64/releases)
- [Changelog](https://github.com/rust-osdev/x86_64/blob/master/Changelog.md)
- [Commits](rust-osdev/x86_64@v0.12.2...v0.12.3)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

Cargo.lock

@@ -25,7 +25,7 @@ integration_tests = []
 
 [dependencies]
 bitflags = "1.2"
-x86_64 = "0.12.2"
+x86_64 = "0.12.3"
 atomic_refcell = "0.1"
 r-efi = "3.2.0"
 uart_16550 = "0.2.10"