x86/fpu, crypto x86/sha256_ssse3: Simplify the sha256_ssse3_mod_init() xfeature checks

Use the new 'cpu_has_xfeatures()' function to query AVX CPU support.

This has the following advantages to the driver:

 - Decouples the driver from FPU internals: it's now only using <asm/fpu/api.h>.

 - Removes detection complexity from the driver, no more raw XGETBV instruction

 - Shrinks the code a bit.

 - Standardizes feature name error message printouts across drivers

There are also advantages to the x86 FPU code: once all drivers
are decoupled from internals we can move them out of common
headers and we'll also be able to remove xcr.h.

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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/crypto/sha256_ssse3_glue.c

@@ -38,8 +38,6 @@
 #include <crypto/sha.h>
 #include <crypto/sha256_base.h>
 #include <asm/fpu/api.h>
-#include <asm/xcr.h>
-#include <asm/fpu/xstate.h>
 #include <linux/string.h>
 
 asmlinkage void sha256_transform_ssse3(u32 *digest, const char *data,
@@ -132,15 +130,9 @@ static struct shash_alg algs[] = { {
 #ifdef CONFIG_AS_AVX
 static bool __init avx_usable(void)
 {
-	u64 xcr0;
-
-	if (!cpu_has_avx || !cpu_has_osxsave)
-		return false;
-
-	xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
-	if ((xcr0 & (XSTATE_SSE | XSTATE_YMM)) != (XSTATE_SSE | XSTATE_YMM)) {
-		pr_info("AVX detected but unusable.\n");
-
+	if (!cpu_has_xfeatures(XSTATE_SSE | XSTATE_YMM, NULL)) {
+		if (cpu_has_avx)
+			pr_info("AVX detected but unusable.\n");
 		return false;
 	}