[U-Boot] [PATCH] Make cmd_get_data_size() a dependency of setexpr

This commit broke the command setexpr.

http://git.denx.de/?p=u-boot.git;a=commit;h=6f62d7c4f7a2242a76e19b09dccca6f6...

setexpr uses cmd_get_data_size(). If none of I2C, ITEST or PCI is chosen, setexpr will fail to be built.