efi/libstub: Fix gcc error around __umoddi3 for 32 bit builds

32bit gcc doesn't support modulo operation on 64 bit data. It results in
a __umoddi3 error while building EFI for 32 bit.

Use bitwise operations instead of modulo operations to fix the issue.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Link: https://lore.kernel.org/r/20200625234516.31406-2-atish.patra@wdc.com
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/alignedmem.c

@@ -44,7 +44,7 @@ efi_status_t efi_allocate_pages_aligned(unsigned long size, unsigned long *addr,
 	*addr = ALIGN((unsigned long)alloc_addr, align);
 
 	if (slack > 0) {
-		int l = (alloc_addr % align) / EFI_PAGE_SIZE;
+		int l = (alloc_addr & (align - 1)) / EFI_PAGE_SIZE;
 
 		if (l) {
 			efi_bs_call(free_pages, alloc_addr, slack - l + 1);