MdeModulePkg/DebugSupportDxe: Fix XCODE5 build failure
MdeModulePkg/DebugSupportDxe: Fix XCODE5 build failure

https://bugzilla.tianocore.org/show_bug.cgi?id=572

Update X64 AsmFuncs.S to resolve a build failure using the
XCODE5 tool chain.  This change updates AsmFuncs.S to match
AsmFuncs.asm and AsmFuncs.nasm.

The error generated in XCODE5 build is:

error: invalid instruction mnemonic 'movzxw'
    movzxw 8(%rax), %rax
    ^~~~~~

The correct instruction is

    movzwq 8(%rax), %rax

Cc: Star Zeng <5c6bb72efe464613af94e84c05522a361b23844a@intel.com>
Cc: Eric Dong <fa9eeec52367040ac98013bc4b2913db170588f8@intel.com>
Cc: Andrew Fish <be8d29debaaf5173b4b7ecb4ace852732e71f7b9@apple.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael D Kinney <fd20bc543a9f65bb633fac7d08a403c1f1c8eb6c@intel.com>
Reviewed-by: Andrew Fish <be8d29debaaf5173b4b7ecb4ace852732e71f7b9@apple.com>
Reviewed-by: Star Zeng <5c6bb72efe464613af94e84c05522a361b23844a@intel.com>

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