staging: r8188eu: read pwr seq length, remove PWR_CMD_END

The definitions of the power sequences are in the same file as the function
which processes them. We can simply read the number of entries in a power
sequence. There's no need for a PWR_CMD_END command to indicate the end
of a sequence.

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220704145221.159949-4-martin@kaiser.cx


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>