cmake: fix typo

Fixes: fce9382b4b99 ("cmake: Check for getrandom system call")
Signed-off-by: Felix Fietkau <nbd@nbd.name>

CMakeLists.txt

@@ -17,7 +17,7 @@ IF(DEBUG)
 ENDIF()
 
 INCLUDE (CheckSymbolExists)
-CHECK_SYMBOL_EXISTS(SYS_getrandom sycall.h getrandom)
+CHECK_SYMBOL_EXISTS(SYS_getrandom syscall.h getrandom)
 
 IF(getrandom)
   ADD_EXECUTABLE(getrandom getrandom.c)