x86/mtrr: Remove unused cyrix_set_all() function

The Cyrix CPU specific MTRR function cyrix_set_all() will never be
called as the mtrr_ops->set_all() callback will only be called in the
use_intel() case, which would require the use_intel_if member of struct
mtrr_ops to be set, which isn't the case for Cyrix.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20221004081023.32402-3-jgross@suse.com