x86/fpu: Rename fpu_init() to fpu__cpu_init()

fpu_init() is a bit of a misnomer in that it (falsely) creates the
impression that it's related to the (old) fpu_finit() function,
which initializes FPU ctx state.

Rename it to fpu__cpu_init() to make its boot time initialization
clear, and to move it to the fpu__*() namespace.

Also fix and extend its comment block to point out that it's
called not only on the boot CPU, but on secondary CPUs as well.

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
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/kernel/cpu/common.c

@@ -1439,7 +1439,7 @@ void cpu_init(void)
 	clear_all_debug_regs();
 	dbg_restore_debug_regs();
 
-	fpu_init();
+	fpu__cpu_init();
 
 	if (is_uv_system())
 		uv_cpu_init();
@@ -1495,7 +1495,7 @@ void cpu_init(void)
 	clear_all_debug_regs();
 	dbg_restore_debug_regs();
 
-	fpu_init();
+	fpu__cpu_init();
 }
 #endif