uefi-services: Change panic handler log message.

[raccog]

The panic handler now displays its log message using println! instead of error!. The message prefix is altered from [ERROR] to [PANIC]. The extraneous filename and line number printed by error! are also removed from the log message.

Previously, the panic handler in uefi-services would use error! to print a log message. By using error!, the log message would also include the file name and line number of the panic handler function. As the file name and line number where the panic originated from are logged using the PanicInfo struct, this information is not necessary. By printing the log message with println! instead of error! this unnecessary information can be removed.

Example

I temporarily added a panic call to the uefi test runner to show the panic log messages:

    // ...

    // uefi-test-runner/src/main.rs@21
    // Initialize utilities (logging, memory allocation...)
    uefi_services::init(&mut st).expect("Failed to initialize utilities");

    // test a call to panic
    panic!("Here is a panic!");

    // unit tests here

    // output firmware-vendor (CStr16 to Rust string)
    let mut buf = String::new();

    // ...

Log message before this commit:

[ERROR]: uefi-services/src/lib.rs@184: panicked at 'Here is a panic!', uefi-test-runner/src/main.rs:25:5

Log message after commit:

[PANIC]: panicked at 'Here is a panic!', uefi-test-runner/src/main.rs:25:5

Checklist

• Sensible git history (for example, squash "typo" or "fix" commits): See the
  Rewriting History guide for
  help.
• Update the changelog (if necessary)

[nicholasbishop]

LGTM, thanks :)

[raccog]

LGTM, thanks :)

Glad to contribute! :)

[phip1611]

Very nice, thanks for the contribution!