kernel: Introduce external throttling for ASPEED UART

Jeremy Kerr (5):
      serial: expose buf_overrun count through proc interface
      serial: Introduce UPSTAT_SYNC_FIFO for synchronised FIFOs
      serial/8250: export serial8250_read_char
      serial/aspeed-vuart: Implement rx throttling
      serial/aspeed-vuart: Implement quick throttle mechanism

Change-Id: I5165a2981a7198844646a32e5f8f176a6bae4537
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/common/recipes-kernel/linux/linux-obmc_4.13.bb b/common/recipes-kernel/linux/linux-obmc_4.13.bb
index 3699cca..6390c2f 100644
--- a/common/recipes-kernel/linux/linux-obmc_4.13.bb
+++ b/common/recipes-kernel/linux/linux-obmc_4.13.bb
@@ -1,6 +1,6 @@
 KBRANCH ?= "dev-4.13"
 LINUX_VERSION ?= "4.13.16"
 
-SRCREV="101790466fa90d70d475ef015df8aa1527a23a73"
+SRCREV="158c8e15d577cebdb047f5d553e12054b15b1b84"
 
 require linux-obmc.inc