regulator: mcp16502: add enum MCP16502_REG_HPM description

Add description for MCP16502_REG_HPM to prevent a kernel-doc warning:

drivers/regulator/mcp16502.c:90: warning: Enum value 'MCP16502_REG_HPM' not described in enum 'mcp16502_reg'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20230117070139.28905-1-rdunlap@infradead.orgSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/mcp16502.c

@@ -77,6 +77,7 @@
  * @MCP16502_REG_A: active state register
  * @MCP16502_REG_LPM: low power mode state register
  * @MCP16502_REG_HIB: hibernate state register
+ * @MCP16502_REG_HPM: high-performance mode register
  * @MCP16502_REG_SEQ: startup sequence register
  * @MCP16502_REG_CFG: configuration register
  */