OvmfPkg LoadLinuxLib: Use kernel's EFI entry point where available

Usage of the EFI entry point was made feasible in the kernel
x64 boot protocol 2.12 where a 32-bit & 64-bit entry point
became well defined.

http://git.kernel.org/linus/09c205af

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14132 6f19259b-4bc3-4df7-8a09-765794883524

OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.asm

@@ -68,4 +68,28 @@ JumpToKernel PROC
 
 JumpToKernel ENDP
 
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; JumpToUefiKernel (
+;   EFI_HANDLE ImageHandle,        // rcx
+;   EFI_SYSTEM_TABLE *SystemTable, // rdx
+;   VOID *KernelBootParams         // r8
+;   VOID *KernelStart,             // r9
+;   );
+;------------------------------------------------------------------------------
+JumpToUefiKernel PROC
+
+    mov     rdi, rcx
+    mov     rsi, rdx
+    mov     rdx, r8
+    xor     rax, rax
+    mov     eax, [r8 + 264h]
+    add     r9, rax
+    add     r9, 200h
+    call    r9
+    ret
+
+JumpToUefiKernel ENDP
+
 END