Makefile: fix detection of fmc-bus directory

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

Makefile

@@ -2,7 +2,8 @@
 # We have a problem here: this package may be a submodule of something
 # else (for example: fine-delay). If this is the case, fmc-bus is on ../
 # This external script returns the pathname of the "kernel" subdir of fmc-bus
-FMC_DRV ?= $(./check-fmc-bus)
+FMC_DRV ?= $(shell ./check-fmc-bus)
+export FMC_DRV
 
 DIRS = $(FMC_DRV) kernel tools
 

kernel/Makefile

 
 LINUX ?= /lib/modules/$(shell uname -r)/build
 
-FMC_DRV ?= $(shell $M/../check-fmc-bus)
+FMC_DRV ?= $(shell ../check-fmc-bus)
+export FMC_DRV
 
 KBUILD_EXTRA_SYMBOLS := $(FMC_DRV)/Module.symvers