regulator: sm5703: Remove because it is unused and fails to build

regulator: sm5703: Remove because it is unused and fails to build

This file does not compile because <linux/mfd/sm5703.h> is missing.
In KConfig, it depends on MFD_SM5703.

Both MFD_SM5703 and the missing include rely on another patch that never
got merged. The last iteration related to this patch is [1].

So remove this dead-code and undo commit e8858ba89ca3 ("regulator:
sm5703-regulator: Add regulators support for SM5703 MFD")

[1]: https://lore.kernel.org/lkml/20220423085319.483524-5-markuss.broks@gmail.com/

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://patch.msgid.link/0f5da91a05e7343d290c88e3c583b674cf6219ac.1725910247.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Mark Brown <broonie@kernel.org>