powerpc/powernv/idle: Rename pnv_first_spr_loss_level variable

Replace the variable name from using "pnv_first_spr_loss_level" to
"deep_spr_loss_state".

pnv_first_spr_loss_level is supposed to be the earliest state that
has OPAL_PM_LOSE_FULL_CONTEXT set, in other places the kernel uses the
"deep" states as terminology. Hence renaming the variable to be coherent
to its semantics.

Signed-off-by: Pratik Rajesh Sampat <psampat@linux.ibm.com>
Acked-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200721153708.89057-3-psampat@linux.ibm.com