kernel: update and enable full 1GB of RAM on Clearfog Base

I had no idea that I need CONFIG_HIGHMEM to be able to even *see* more
than about 750 MB of RAM on this particular ARM CPU, but hey, here it
goes. (At least there was an info message in dmesg.)

Before:

 # free
               total        used        free      shared  buff/cache   available
 Mem:         769276       47968      407976      269304      313332      438664
 Swap:             0           0           0

Now:

 # free
               total        used        free      shared  buff/cache   available
 Mem:        1029352       49392      894400       43168       85560      913896
 Swap:             0           0           0

Also update to the latest stable (our patches are available as cesnet/2020-04-29).

Change-Id: I6cabd684fcfbe78a2718130ae46ca7f77b4c8228
diff --git a/board/czechlight/clearfog/patches/linux.patch b/board/czechlight/clearfog/patches/linux.patch
index 62b40b0..b5ab6b3 100644
--- a/board/czechlight/clearfog/patches/linux.patch
+++ b/board/czechlight/clearfog/patches/linux.patch
@@ -130,7 +130,7 @@
  	data->ngpio = ngpio;
  
 diff --git a/drivers/spi/spi-orion.c b/drivers/spi/spi-orion.c
-index c7266ef295fd..576bce155456 100644
+index 1f59beb7d27e..afbcc92dcaf8 100644
 --- a/drivers/spi/spi-orion.c
 +++ b/drivers/spi/spi-orion.c
 @@ -88,10 +88,6 @@ struct orion_direct_acc {
@@ -171,7 +171,7 @@
  
  	if (vaddr && xfer->tx_buf && word_len == 8) {
  		unsigned int cnt = count / 4;
-@@ -682,7 +678,6 @@ static int orion_spi_probe(struct platform_device *pdev)
+@@ -681,7 +677,6 @@ static int orion_spi_probe(struct platform_device *pdev)
  	}
  
  	for_each_available_child_of_node(pdev->dev.of_node, np) {
@@ -179,7 +179,7 @@
  		u32 cs;
  		int cs_gpio;
  
-@@ -750,13 +745,14 @@ static int orion_spi_probe(struct platform_device *pdev)
+@@ -749,13 +744,14 @@ static int orion_spi_probe(struct platform_device *pdev)
  		 * This needs to get extended for the direct SPI-NOR / SPI-NAND
  		 * support, once this gets implemented.
  		 */