Replace slub with slab from perf comparison.

SLUB is said to be next generation of SLAB and replacement
for SLAB. But At least in windcharger board, I see serious
page fragmentation: even though similar free memory with SLAB,
but most are 1,2,4 pages region. This results in big page alloc
failures. SLAB is much better.

Change-Id: Ia1be4e022c4fedf6bca4f04ddc43e759d76c83a7
diff --git a/arch/mips/configs/gfwc100_defconfig b/arch/mips/configs/gfwc100_defconfig
index b331fc5..85bdc41 100644
--- a/arch/mips/configs/gfwc100_defconfig
+++ b/arch/mips/configs/gfwc100_defconfig
@@ -18,8 +18,8 @@
 CONFIG_EMBEDDED=y
 CONFIG_PERF_EVENTS=y
 # CONFIG_VM_EVENT_COUNTERS is not set
-# CONFIG_SLUB_DEBUG is not set
 # CONFIG_COMPAT_BRK is not set
+CONFIG_SLAB=y
 CONFIG_MODULES=y
 CONFIG_MODULE_UNLOAD=y
 # CONFIG_SUSPEND is not set