Fix misleading indentation in arm64's identcpu

[dim]

Summary

Clang 10.0.0 produces the following -Werror warning:

sys/arm64/arm64/identcpu.c:1170:5: error: misleading indentation; statement is not part of the previous 'if' [-Werror,-Wmisleading-indentation]
                                break;
                                ^
sys/arm64/arm64/identcpu.c:1168:4: note: previous statement is here
                        if (fv[j].desc[0] != '\0')
                        ^

It appears the break statement is supposed to belong to the if
statement just before it, so add some braces to make it so.

[andrew]

There should be at most one field to print in the inner loop. The break outside the if block is correct, just at the wrong indentation level.

[dim]

Remove braces, and put break after the if statement.