hvm svm: Avoid intercepts when accessing a number of architectural MSRs.

hvm svm: Avoid intercepts when accessing a number of architectural MSRs.

1. Removes intercept of guest-specific MSRs
MSR_IA32_SYSENTER_{CS,ESP,EIP}, MSR_{L,C,}STAR, MSR_SYSCALL_MASK,
MSR_SHADOW_GS_BASE.

2. Removes code to deal with those intercepts, as well as the
FS/GS-base. Since long_mode_do_msr_read now became essentially a
switch of a single case + default, I removed the entire function and
inlined the remaining single case-statement into the original
MSR-access function.

Signed-off-by: Mats Petersson <mats.petersson@amd.com>