Documentation: core-api: entry: Fix typo "systcalls" -> "syscalls"

Fix a typo: "systcalls" should be "syscalls".

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250715061529.56268-1-ajd@linux.ibm.com

Author: ajdlinux

Documentation/core-api/entry.rst

@@ -105,7 +105,7 @@ has to do extra work between the various steps. In such cases it has to
 ensure that enter_from_user_mode() is called first on entry and
 exit_to_user_mode() is called last on exit.
 
-Do not nest syscalls. Nested systcalls will cause RCU and/or context tracking
+Do not nest syscalls. Nested syscalls will cause RCU and/or context tracking
 to print a warning.
 
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