drivers: fix section mismatch in qcom's regulator drivers

Section mismatch was warned after upstream commit 1b9980fb24
finally fixed modpost's ability to detect EXPORT_SYMBOL plus __init
or __exit. Qcom's qpnp and stub regulator drivers have both __init
and EXPORT_SYMBOL.

- This particular 4.9 kernel does not build anything into modules.
- Currently I do not see any code using qpnp_regulator_init or
  regulator_stub_init outside its own translation unit.

Therefore, similar to d336e9a71e, just unexport the symbol.

Also, according to the kernel-hacking doc [1], "it makes no sense
for a function marked with __init to be exported to modules with
EXPORT_SYMBOL() or EXPORT_SYMBOL_GPL()" because functions marked
with __init are dropped after boot is complete.

[1] https://docs.kernel.org/kernel-hacking/hacking.html#init-exit-initdata

Signed-off-by: Chenyang Zhong <zhongcy95@gmail.com>

drivers/regulator/qpnp-regulator.c

@@ -2423,7 +2423,6 @@ int __init qpnp_regulator_init(void)
 
 	return platform_driver_register(&qpnp_regulator_driver);
 }
-EXPORT_SYMBOL(qpnp_regulator_init);
 
 static void __exit qpnp_regulator_exit(void)
 {

drivers/regulator/stub-regulator.c

@@ -293,7 +293,6 @@ int __init regulator_stub_init(void)
 
 	return platform_driver_register(&regulator_stub_driver);
 }
-EXPORT_SYMBOL(regulator_stub_init);
 postcore_initcall(regulator_stub_init);
 
 static void __exit regulator_stub_exit(void)