x86/fpu: Calculate the default sizes independently

When dynamically enabled states are supported the maximum and default sizes
for the kernel buffers and user space interfaces are not longer identical.

Put the necessary calculations in place which only take the default enabled
features into account.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211021225527.10184-22-chang.seok.bae@intel.com