x86/boot/e820: Fix typo in e820.c comment

change "itsmain" to "its main".

Fixes: 544a0f47 ("x86/boot/e820: Rename e820_table_saved to e820_table_firmware and improve the description")
Signed-off-by: Wang Yong <yongw.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20221211103849.173870-1-yongw.kernel@gmail.com

arch/x86/kernel/e820.c

@@ -53,7 +53,7 @@
  *
  * Once the E820 map has been converted to the standard Linux memory layout
  * information its role stops - modifying it has no effect and does not get
- * re-propagated. So itsmain role is a temporary bootstrap storage of firmware
+ * re-propagated. So its main role is a temporary bootstrap storage of firmware
  * specific memory layout data during early bootup.
  */
 static struct e820_table e820_table_init		__initdata;