packaging: Use the u-boot.spec for u-boot-rpi4-32b

packaging: Use the u-boot.spec for u-boot-rpi4-32b

xu3 didn't support anymore on Tizen. So it doesn't need to build
anymore. Instead, move the u-boot-rpi4-32b into u-boot.spec.
It will be created same rpm packages like below.

- u-boot-rpi4-32b-2024.10-0.armv7l.rpm
- u-boot-rpi4-32b-debugsource-2024.10-0.armv7l.rpm
- u-boot-tools-2024.10-0.armv7l.rpm
- u-boot-tools-debuginfo-2024.10-0.armv7l.rpm

Change-Id: If53dce0db499137396380bd8c6d3a8c39b2c12e6
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>