efi_loader: make variable store size customizable

Currently the size of the buffer to keep UEFI variables in memory is fixed
at 16384 bytes. This size has proven to be too small for some use cases.

Make the size of the memory buffer for UEFI variables customizable.

Reported-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/include/efi_variable.h b/include/efi_variable.h
index 4704a3c..bf50762 100644
--- a/include/efi_variable.h
+++ b/include/efi_variable.h
@@ -91,7 +91,7 @@
 
 #define EFI_VAR_FILE_NAME "ubootefi.var"
 
-#define EFI_VAR_BUF_SIZE 0x4000
+#define EFI_VAR_BUF_SIZE CONFIG_EFI_VAR_BUF_SIZE
 
 /*
  * This constant identifies the file format for storing UEFI variables in