fix stack overread on truncated range in cpulist parse_entry

[soma0212]

parse_entry dereferences number_start without checking that anything actually follows the '-':

• cpuinfo_linux_parse_cpulist hands it entry_end == &buffer[BUFFER_SIZE] whenever a full read turns up no ',', since the leftover then gets reparsed as one entry spanning the whole buffer
• an entry ending in '-' leaves number_start at entry_end, parse_number consumes nothing, and the failure branch reads *number_start, which is buffer[256]
• cpuinfo_log_warning is an inline static variadic function, so that argument is evaluated whatever CPUINFO_LOG_LEVEL is set to
• ASan calls it a 1-byte stack-buffer-overflow read at cpulist.c:119 on a cpu list of 255 digits followed by '-'

Bailing out before the dereference leaves the entry rejected exactly as it already was, so the callback sequence and return value are the same on every input I tried, valid or malformed.

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