eal/x86: fix some CPU extended features definitions

eal/x86: fix some CPU extended features definitions

Caught while checking CPUID related stuff in OVS.

According to [1], for Structured Extended Feature Flags Enumeration Leaf
(EAX = 0x07H, ECX = 0):

- BMI1 is associated to EBX, bit 3 (was incorrectly 2),
- SMEP is associated to EBX, bit 7 (was incorrectly 6),
- BMI2 is associated to EBX, bit 8 (was incorrectly 7),
- ERMS is associated to EBX, bit 9 (was incorrectly 8),

1: https://software.intel.com/sites/default/files/managed/c5/15/architecture-instruction-set-extensions-programming-reference.pdf

Fixes: af75078fece3 ("first public release")
Cc: stable@dpdk.org
Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>