fpga: altera-pr-ip: fix unsigned comparison with less than zero

Fix the "comparison with less than zero" warning reported by
cppcheck for the unsigned (size_t) parameter count of the
alt_pr_fpga_write() function.

Fixes: d201cc17a8a3 ("fpga pr ip: Core driver support for Altera Partial Reconfiguration IP")
Reviewed-by: Tom Rix <[e-mail]>
Acked-by: Xu Yilun <[e-mail]>
Signed-off-by: Marco Pagani <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Xu Yilun <[e-mail]>

drivers/fpga/altera-pr-ip-core.c

···
 	u32 *buffer_32 = (u32 *)buf;
 	size_t i = 0;
 
-	if (count <= 0)
+	if (!count)
 		return -EINVAL;
 
 	/* Write out the complete 32-bit chunks */