pseries/papr-hvpipe: Fix & simplify error handling in papr_hvpipe_init()

Remove such 3 levels of nesting patterns to check success return values
from function calls.

ret = enable_hvpipe_IRQ()
    if (!ret)
	    ret = set_hvpipe_sys_param(1)
	        if (!ret)
		    ret = misc_register()

Instead just bail out to "out*:" labels, in case of any error. This
simplifies the init flow.

While at it let's also fix the following error handling logic:
We have already enabled interrupt sources and enabled hvpipe to received
interrupts, if misc_register() fails, we will destroy the workqueue, but
the HMC might send us a msg via hvpipe which will call, queue work on
the workqueue which might be destroyed.

So instead, let's reverse the order of enabling set_hvpipe_sys_param(1)
and in case of an error let's remove the misc dev by calling
misc_deregister().

Cc: stable@vger.kernel.org
Fixes: 39a08a4f94980 ("powerpc/pseries: Enable hvpipe with ibm,set-system-parameter RTAS")
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/f2141eafb80e7780395e03aa9a22e8a37be80513.1777606826.git.ritesh.list@gmail.com

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