x86: remove duplicate #define from 'cpufeature.h'

Impact: cleanup

Remove duplicate #define from 'cpufeature.h'.

This also fixes the following sparse warning:

 arch/x86/kernel/cpu/capflags.c:54:3: warning: Initializer entry defined twice
 arch/x86/kernel/cpu/capflags.c:58:3:   also defined here

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>