MdePkg/BaseLib AARCH64: Make asm files BTI compatible

Add the BTI instructions and the associated note to make the AArch64 asm
objects compatible with BTI enforcement.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>
Reviewed-by: Oliver Smith-Denny <osd@smith-denny.com>

MdePkg/Library/BaseLib/AArch64/SwitchStack.S

@@ -35,6 +35,7 @@ GCC_ASM_EXPORT(CpuPause)
 #  );
 #
 ASM_PFX(InternalSwitchStackAsm):
+    AARCH64_BTI(c)
     mov   x29, #0
     mov   x30, x0
     mov   sp, x3
@@ -57,6 +58,7 @@ ASM_PFX(InternalSwitchStackAsm):
 #  )
 #
 ASM_PFX(CpuPause):
+    AARCH64_BTI(c)
     nop
     nop
     nop