efi/libstub: Export efi_low_alloc_above() to other units

Permit arm32-stub.c to access efi_low_alloc_above() in a subsequent
patch by giving it external linkage and declaring it in efistub.h.
Reviewed-by: Maxim Uvarov <maxim.uvarov@linaro.org>
Tested-by: Maxim Uvarov <maxim.uvarov@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/efistub.h

@@ -740,6 +740,9 @@ efi_status_t efi_allocate_pages(unsigned long size, unsigned long *addr,
 efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr,
 					unsigned long max, unsigned long align);
 
+efi_status_t efi_low_alloc_above(unsigned long size, unsigned long align,
+				 unsigned long *addr, unsigned long min);
+
 efi_status_t efi_relocate_kernel(unsigned long *image_addr,
 				 unsigned long image_size,
 				 unsigned long alloc_size,

drivers/firmware/efi/libstub/relocate.c

@@ -20,8 +20,8 @@
  *
  * Return:	status code
  */
-static efi_status_t efi_low_alloc_above(unsigned long size, unsigned long align,
-					unsigned long *addr, unsigned long min)
+efi_status_t efi_low_alloc_above(unsigned long size, unsigned long align,
+				 unsigned long *addr, unsigned long min)
 {
 	unsigned long map_size, desc_size, buff_size;
 	efi_memory_desc_t *map;