The 'KERNEL' is not referenced by other objects, so double '$$' will
cause shell unable to parse the variable 'BLOCKSIZE':
dd ... bs=$(BLOCKSIZE) conv=sync
bash: line 1: BLOCKSIZE: command not found
Fixes: 09a0efbe83(ramips: set default BLOCKSIZE to 64k for nor flash devices)
Signed-off-by: Shiji Yang <yangshiji66@qq.com>
ab7e251303