This patch fixes the MISRA-C violations in arch/x86/vmcs.c.
* make the function have only one exit point
v1 -> v2:
* update 'is_cr0_write_valid' and 'is_cr4_write_valid'
use `if ... else` rather than check 'ret' value
Tracked-On: #861
Signed-off-by: Shiqing Gao <shiqing.gao@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>