OvmfPkg/Qemu: Fix various typos

Fix various typos in comments and documentation.

When "VbeShim.asm" is modified, we have to re-run "VbeShim.sh"
to update "VbeShim.h".
The string modified by this patch is only used when the DEBUG
macro (at the top of the file) is commented out. Since the
string is not referenced, NASM eliminates it, resulting in
the same byte array content in "VbeShim.h".

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Antoine Coeur <coeur@gmx.fr>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Philippe Mathieu-Daude <philmd@redhat.com>
Message-Id: <20200207010831.9046-58-philmd@redhat.com>

OvmfPkg/QemuVideoDxe/VbeShim.asm

@@ -49,7 +49,7 @@ Handler:
   je         ReadEdid
   cmp        ah, 0x00
   je         SetModeLegacy
-  DebugLog   StrUnkownFunction
+  DebugLog   StrUnknownFunction
 Hang:
   jmp        Hang
 
@@ -93,7 +93,7 @@ GetModeInfo:
   and        cx, ~0x4000 ; clear potentially set LFB bit in mode number
   cmp        cx, 0x00f1
   je         KnownMode1
-  DebugLog   StrUnkownMode
+  DebugLog   StrUnknownMode
   jmp        Hang
 KnownMode1:
   ; target (es:di) set on input
@@ -155,7 +155,7 @@ SetMode:
 
   cmp        bx, 0x40f1
   je         KnownMode2
-  DebugLog   StrUnkownMode
+  DebugLog   StrUnknownMode
   jmp        Hang
 KnownMode2:
 
@@ -203,7 +203,7 @@ SetModeLegacy:
   je         KnownMode3
   cmp        al, 0x12
   je         KnownMode4
-  DebugLog   StrUnkownMode
+  DebugLog   StrUnknownMode
   jmp        Hang
 KnownMode3:
   mov        al, 0x30
@@ -252,7 +252,7 @@ StrExitSuccess:
 StrExitUnsupported:
   db 'Unsupported', 0x0a, 0
 
-StrUnkownFunction:
+StrUnknownFunction:
   db 'Unknown Function', 0x0a, 0
 
 StrEnterGetInfo:
@@ -270,8 +270,8 @@ StrEnterSetMode:
 StrEnterSetModeLegacy:
   db 'SetModeLegacy', 0x0a, 0
 
-StrUnkownMode:
-  db 'Unkown Mode', 0x0a, 0
+StrUnknownMode:
+  db 'Unknown Mode', 0x0a, 0
 
 StrGetPmCapabilities:
   db 'GetPmCapabilities', 0x0a, 0