x86/fpu: Use XFEATURE_FP/SSE enum values instead of hardcoded numbers

When setting up sizes and offsets for legacy header entries the code uses
hardcoded 0/1 instead of the corresponding enum values XFEATURE_FP and
XFEATURE_SSE.

Replace the hardcoded numbers which enhances readability of the code and
also makes this code the first user of those enum values..

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191101130153.GG1615@uranus.lan