x86/fpu, crypto: Fix AVX2 feature tests

For some CPU models I broke the AVX2 feature detection in:

  7bc371fa ("x86/fpu, crypto x86/camellia_aesni_avx2: Simplify the camellia_aesni_init() xfeature checks")
  534ff06e ("x86/fpu, crypto x86/serpent_avx2: Simplify the init() xfeature checks")

... because I did not realize that it's possible for a CPU to support
the xstate necessary for AVX2 execution (XSTATE_YMM), but not have
the AVX2 instructions themselves.

Restore the necessary CPUID checks as well.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>