[U-Boot] Export redesign

[Martin Dorwig]

Hello, 

for CONFIG_AVR32 the macro looks like this:
#define EXPORT_FUNC(x)					\
	asm volatile(					\
		"	.globl\t" #x "\n"		\
		#x ":\n"				\
		"	ld.w	r8, r6[%0]\n"		\
		"	ld.w	pc, r8[%1]\n"		\
		:					\
		: "i"(offsetof(gd_t, jt)), "i"(XF_ ##x)	\
		: "r8");
if there is an implicit shift in the ld.w instructuions, then the 
ld.w r8,r6[%0] is wrong, because offsetof(gd_t, jt) is the offset in bytes.
if there is no shift, then the 
ld.w pc,r8[%1] is wrong, because the XF_ ## is not multiplied by sizeof(void*)

the syntax from the avr32 manual shows

Operation:
III. Rd ← *(Rp + (ZE(disp5) << 2));
IV. Rd ← *(Rp + (SE(disp16)));

Syntax:
III.  ld.w Rd, Rp[disp]
IV.  ld.w Rd, Rp[disp]

my interpretation is :
the assembler checks if (disp % 4 == 0) && disp <= 124 then
is uses variant III and places disp >> 2 as disp5 into the instruction.
else it uses variant IV and places disp as disp16 into the 
extension word of the instruction.


Regards
Martin