Add config option for CONFIG_RESET_CHUNK_BITS

The config variable is used in the kernel but no setting was provided
prio to this commit.

Kconfig

@@ -348,6 +348,12 @@ menu "seL4 System Parameters"
             the kernel checks for pending interrupts (and preempts the
             currently running syscall if interrupts are pending).
 
+    config RESET_CHUNK_BITS
+        int "Max chunks to reset when clearing memory"
+        default 8
+        help
+            Maximum size in bits of chunks of memory to zero before checking a preemption point.
+
     config MAX_NUM_BOOTINFO_UNTYPED_CAPS
         int "Max number of bootinfo untyped caps"
         default 167

config.cmake

@@ -83,6 +83,11 @@ config_string(KernelMaxNumWorkUnitsPerPreemption MAX_NUM_WORK_UNITS_PER_PREEMPTI
     DEFAULT 100
     UNQUOTE
 )
+config_string(KernelResetChunkBits RESET_CHUNK_BITS
+    "Maximum size in bits of chunks of memory to zero before checking a preemption point."
+    DEFAULT 8
+    UNQUOTE
+)
 config_string(KernelMaxNumBootinfoUntypedCaps MAX_NUM_BOOTINFO_UNTYPED_CAPS
     "Max number of bootinfo untyped caps"
     DEFAULT 230