KVM: x86: Rename vmx_vmentry/vmexit_ctrl() helpers

KVM: x86: Rename vmx_vmentry/vmexit_ctrl() helpers

Rename the two helpers vmx_vmentry/vmexit_ctrl() to
vmx_get_initial_vmentry/vmexit_ctrl() to represent their real meaning.

No functional change intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
Tested-by: Xudong Hao <xudong.hao@intel.com>
Link: https://lore.kernel.org/r/20250806195706.1650976-23-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>