i386: fix setCx86/getCx86 race in macros

i386: fix setCx86/getCx86 race in macros

Because of the way the setCx86 macro is defined, a call to
setCx86(XXXX, getCx86(XXXX)) will produce the wrong output sequence.
This affects at least one place in arch/i386/kernel/setup.c :

	/* Enable MMX extensions (App note 108) */
	setCx86(CX86_CCR7, getCx86(CX86_CCR7)|1);

A correct solution consists in passing the value argument via a
temporary variable. 2.6 has a different fix using inline functions,
which produce equivalent code though.

Signed-off-by: Willy Tarreau <w@1wt.eu>