tcg/tci: Restrict tci_write_reg16() to 64-bit hosts

Restrict tci_write_reg16() to 64-bit hosts to fix on 32-bit ones:

  [520/1115] Compiling C object libqemu-arm-linux-user.fa.p/tcg_tci.c.o
  FAILED: libqemu-arm-linux-user.fa.p/tcg_tci.c.o
  tcg/tci.c:132:1: error: 'tci_write_reg16' defined but not used [-Werror=unused-function]
   tci_write_reg16(tcg_target_ulong *regs, TCGReg index, uint16_t value)
   ^~~~~~~~~~~~~~~

Fixes: 2f160e0f979 ("tci: Add implementation for INDEX_op_ld16u_i64")
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Stefan Weil <sw@weilnetz.de>
Message-Id: <20210123094107.2340222-1-f4bug@amsat.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
diff --git a/tcg/tci.c b/tcg/tci.c
index 2311aa7..3fc82d3 100644
--- a/tcg/tci.c
+++ b/tcg/tci.c
@@ -128,11 +128,13 @@
     tci_write_reg(regs, index, value);
 }
 
+#if TCG_TARGET_REG_BITS == 64
 static void
 tci_write_reg16(tcg_target_ulong *regs, TCGReg index, uint16_t value)
 {
     tci_write_reg(regs, index, value);
 }
+#endif
 
 static void
 tci_write_reg32(tcg_target_ulong *regs, TCGReg index, uint32_t value)